
Hichard A. Proctor. 



'OX 



& 






INTRODUCTORY NOTE. 



*l 



This book had from the first a very extraordinary sua 
cess. It appeared in 1870, and at once attracted the 
attention of the scientific world and of all who were inter- 
ested in knowing what the telescope and the spectroscope 
have revealed to the tireless gaze of science. The volume 
is written in a most charming style. Like Huxley and 
Tyndall, Mr. Proctor sees the poetry of his subject and 
knows how to bring the largest truths within the com- 
prehension of a child, and make the deepest researches 
as interesting to the general reader as a novel. What the 
earth teaches us, what we learn from the sun, Mars a 
miniature earth, Jupiter the giant of our system, the 
nature of nebulae, the constitution and shape of the uni- 
verse, the probability that other worlds are inhabited — ■ 
such are his themes, and he brings to their discussion all 
the knowledge of one of the profoundest mathematicians 
and astronomers of this age, and all the power of a poet 
on the perception and expression of beauty. 

Eichard A. Proctor was bom in England in 1837. He 
enjoyed a liberal education and distinguished himself in 
his boyhood as a fine student. In 1866 he lost his fortune 



6 INTRODUCTORY NOTE. 

by the failure of a bank. This hindered his scientific 
work for a time, but his many popular writings soon re- 
lieved him from embarrassment. In 1869 he made sug- 
gestions to Sir George Airy, the astronomer royal, as to 
the best method of observing the coming transit of Yenus, 
and at a meeting of the principal astronomers of England, 
at the Greenwich Observatory, in 1873, his views were 
unanimously approved. In the same year Mr. Proctor 
lectured in America. He came to an untimely death in 
New York, from cholera caught in Florida. 

Frank Parsons. 



FROM THE 

PEEFAOE TO THE FOUETH EDITION. 



This edition has been carefully revised and in many 
important respects modified. 

Several passages relating to questions which were 
under controversy when the earlier editions appeared 
have been removed — those questions having been decid- 
ed by new evidence, in the sense advocated in the orig- 
inal text. 

I have also omitted several passages from the last chap- 
ter, as expressing a more confident opinion about mat- 
ters connected with the supervision and control of the 
universe than I at present entertain. 

BlCHAKD A. PkOCTOB, 



FROM THE 

PKEFAOE TO THE SECOND EDITION. 



Among the additions which have been made to the 
matter contained in a former edition are two which 
require some notice. 

The first consists of new evidence against the theory 
that the cloud-belts of Jupiter and Saturn are raised by 
the sun's heat. I find it difficult to conceive how this 
evidence can be interpreted otherwise than by the theory 
that the belts of the giant planets are generated, main- 
tained, and modified by forces inherent in those planets, 
and not by any action exerted from without. 

The second is the matter contained in pp. 276, 277, 
286-291, and illustrated by the large plate facing p. 288. 
Rightly understood, the evidence there presented is con- 
clusive in favor of the two theses, that — 

1. Within the limits which include the stars visible to 
{he naked eye there are laivs of aggregation and segregation 
'which the theories hitherto accepted respecting the fixed stars 
wholly fail to accotmt for. 

2. The Milky Way is not, as has been so long supposed, 



10 PREFACE. 

a stratum of stars of all orders extending to distances very 
far exceeding, relatively as well as positively, the distances 
of the lucid stars — hut is a stream of small stars, amid 
which many of the lucid stars are immersed. 

These points seem to be as completely demonstrated 
by the evidence adduced as relations of the sort can 
ever be. 

BlCHAKD A. PeOCTOE. 

London, October, 1870. 



EXTRACTS FROM THE 

PEEFAOE TO THE FIEST EDITIOK 



On many of the subjects dealt with in this work, 1 
have propounded views which differ from those usually 
accepted. Each of the new views here presented has 
been the result of a careful study of the subject dealt with, 
and I have searched as anxiously for considerations op- 
posed to any novel theory as for arguments in its favor. 

My theory respecting the sidereal system has been based 
on the signs of systematic aggregation among the lucid 
stars, and of a more intimate association of those stars 
with the Milky Way than could be expected were Sir 
William Herschel's fundamental theory correct. 

The theory brought forward in the chapter on Meteors 
and Comets is not altogether new. The general idea on 
which it is grounded has been dealt with by Mayer and 
Thomson. The idea, however, presented itself independ- 
ently to my mind when I was writing my treatise on 
Saturn. The line of reasoning is wholly new, I believe, 
by which I have endeavored to show that those peculiar- 
ities of the solar system which have hitherto been regarded 



12 PREFACE. 

as affording the strongest objection to the hypothesis of 
development, may be regarded as in reality the direct 
result of the processes by which the solar system has 
reached its present condition. In the preface to my trea- 
tise on Saturn I touched on the possibility that some such 
explanation of those peculiarities might be found, re- 
marking that in the rings of Saturn astronomers may 
one day recognize the action of the processes by which 
the solar system has attained its present state. 

RlCHAED A. PeOOTOR. 

London, May, 1870. 



CONTENTS. 



Introduction, • • • . it 

CHAPTER L 
What Our Earth Teaches Us, . « , • • • .21 

CHAPTER H. 
What We Learn from the Sun, . • • • ,84 

CHAPTER ILL 
The Inferior Planets, .... • • • • 69 

CHAPTER IV. 
Mars, the Miniature of Our Earth, . • • • • 95 

CHAPTER V. 
Jupiter, the Giant of the Solar System, • • 120 

CHAPTER VL 
Saturn, the Ringed World, ..••••• 159 

CHAPTER VII. 
Uranus and Neptune, the Arctic Planets, . . ,176 

CHAPTER VIII. 
las Moon and Other Satellites, . ... 187 



14 CONTENTS. 

CHAPTER IX. 
Meteors and Comets: Their Oppice in the Solar Sts- pagb 
tem, 203 

CHAPTER X. 
Other Suns than Ours, • . 232 

CHAPTER XI. 

Op Minor Stars, and op the Distribution op Stars in 

Space, 261 

CHAPTER XII. 
The Nebula: Are They External Galaxies? . . . 294 

CHAPTER XIII. 
Supervision and Control, ....... 32? 



INTEODTTCTKXN". 



Astronomy and geology owe much of their charm to 
the fact that they suggest thoughts of other forms of life 
than those with which we are familiar. Geology teaches 
us of days when this earth was peopled with strange 
creatures such as now are not found upon its surface. We 
turn our thoughts to the epochs when those monsters 
throve and multiplied, and picture to ourselves the ap- 
pearance which our earth then presented. Strange forms 
of vegetation clothe the scene which the mind's eye 
dwells upon. The air is heavier laden with moisture to 
nourish the abundant flora ; hideous reptiles crawl over 
their slimy domain, battling with each other or with the 
denizens of the forest; huge bat-like creatures sweep 
through the dusky twilight which constituted the prim- 
eval day; weird monsters pursue their prey amid the 
ocean depths : and we forget, as we dwell upon the 
strange forms which existed in those long-past ages, that 
the scene now presented by the earth is no less wonder- 
ful, and that the records of our time may perhaps seem 
one day as perplexing as we now find those of the geo- 
logical eras. 



18 INTRODUCTION. 

Astronomy has a kindred charm. We cannot indeed 
examine the actual substance of living creatures existing 
upon other celestial bodies ; we cannot picture to our- 
selves their appearance or qualities; and only in a few 
instances can we even form any conception of the condi- 
tions under which they live. But we see proofs on all 
sides that, besides the world on which we live, other 
worlds exist as well cared for and as nobly planned. Nay, 
we see globes by the side of which our earth would seem 
but as a tiny speck ; we trace these globes as they sweep 
with stately motion on their appointed courses ; we watch 
the return of day on the broad expanse of their surface ; 
and we see systems of satellites which are suspended as 
lights for their nocturnal skies. We further find that our 
sun is matched by a thousand thousand suns amid the 
immeasurable depths of space; and the mind's eye pic- 
tures other worlds like those which course around the 
sun, travelling in stately orbits around his fellow-lumi- 
naries. 

Long, however, before the wonders of modern astron- 
omy had been revealed to us, men of inquiring minds 
seem to have been led, as by an irresistible instinct, to 
examine into the resemblance which may exist between 
our world and other worlds surrounding it on every side. 
It has not been the mere fanciful theorizer who has dis- 
cussed such questions, but men of the highest eminence 
in science. In long-past ages Anaximander and Pytha- 
goras studied the subject of other worlds than ours; 



INTRODUCTION. 19 

later, such men as Huyghens, Galileo, and Newton have 
dwelt upon the same interesting theme; while, in our 
own day, Whewell and Brewster have employed their sci- 
entific and dialectic skill in defending rival theories upon 
the subject. 

Undoubtedly, a large share of the interest with which 
the question of other worlds than ours has been regarded 
is due to the fact that, as the science of astronomy has 
progressed, the subject has continually presented itself 
under new aspects. The question, in fact, is one of those 
which are ever new and ever old. It has all the charm 
belonging to subjects which men in all ages have de- 
lighted to discuss, while it is associated in the most inti- 
mate manner with the progress of modern scientific re- 
search. The discoveries which are made by astronomers 
acquire a new interest when they are associated with the 
subject of life in other worlds. The interest with which 
the public regard many of those discoveries may, indeed, 
be said to depend wholly on their bearing upon the 
subject. 

"We stand in a position much more favorable for the 
formation of just views on the subject of life in other 
worlds than that from which men surveyed the planetary 
and stellar systems thirty or forty years since. Never, 
since men first explored the celestial depths, has a series 
of more startling discoveries rewarded the labors of as- 
tronomers and physicists than during the past few years. 
Unhoped-for revelations have been made on every side. 



20 INTRODUCTION. 

Analogies the most interesting have brought the distant 
orbs of heaven into close relationship with our own earth, 
or with the central luminary of the planetary scheme. 
And a lesson has been taught us which bears even more 
significantly on our views respecting the existence of 
other worlds : we have learned to recognize within the 
solar system, and within the wondrous galaxy of which 
our sun is a constituent orb, a variety of structure and a 
complexity of detail, of which but a few years ago astron- 
omers had formed but the most inadequate conceptions. 

My object, then, in the pages which follow, is not 
solely to establish the thesis that there are other worlds 
than ours, but to present, in a new and, I hope, interest- 
ing light the marvellous discoveries which have rewarded 
recent scientific researches. Judged merely according to 
their direct significance, these discoveries are full of in- 
terest. But it is when we consider them in their relation 
to the existence of other worlds, when we attempt to 
form a conception of the immense varieties of the forms 
of life corresponding to the innumerable varieties of cos- 
mical structure disclosed by modern researches, that we 
recognize their full significance. Although the growth of 
our knowledge is ever accompanied by a proportional 
growth of our estimate of the unknown, we seem already 
entitled to say that we have 

Come on that which is, and caught 
The deep pulsations of the world, 
iEonian music, measuring out 
The steps of time. 



OTHER WORLDS THAN OURS, 



CHAPTEK I. 

WHAT OUR EARTH TEACHES US. 

Before proceeding to consider the various circumstances 
under which the worlds or systems which surround us ap- 
pear to subsist, it may be well to inquire how far we have 
reason to conclude, from the consideration of our own 
earth, that other orbs in space support life. 

It would not be just to argue directly from the fact 
that the earth is inhabited to the conclusion that the other 
planets are inhabited also, nor thence to the conclusion 
that other stars have, like our sun, their attendant worlds, 
peopled with various forms of life. An analogy founded 
on a single instance has no logical force. And it is 
doubtful whether we have not, in the moon, an instance 
which would as effectually serve to support a directly 
opposite conclusion. It seems all but certain, as we shall 
presently have occasion to show, that no part of the 
moon's globe is inhabited by living creatures. Certainly 
she is inhabited by none which bear the least resemblance 
to those existing on our earth. Thus it might fairly be 



22 OTHER WORLDS THAN OURS. 

urged that, since one of the two orbs respecting which 
we know most appears to be uninhabited, there remains 
no probable argument in favor of the view that other orbs 
besides our earth are the abode of living creatures. Yet 
the earth in reality supplies an argument of great force, 
when we consider the evidence she presents in another 
light. The mere fact that this world is inhabited is, as 
we have seen, little ; but we shall find that the way in 
which life is distributed over the earth's surface is full of 
significance. 

If we range over the earth, from the Arctic regions to 
the torrid zone, we find that none of the peculiarities 
which mark the several regions of our globe suffice to 
banish life from its surface. In the bitter cold within the 
Arctic Circles, with their strange alternations of long sum- 
mer days and long winter nights, their frozen seas, peren- 
nial ice, and scanty vegetation, life flourishes in a hun- 
dred various forms. On the other hand, the torrid zone, 
with its blazing heat, its long-continued droughts, its 
strange absence of true seasonal changes, and its trying 
alternations of oppressive calms and fiercely raging hurri- 
canes, nourishes even more numerous and more various 
forms of life than either of the great temperate zones. 
Around mountain summits as in the depth of the most 
secluded valleys, in mid-ocean as in the arid desert, in the 
air as beneath the surface of the earth, we find a myriad 
forms of life. 

But this is far from being all. Various as are the 



WHAT OUR EARTH TEACHES US. 23 

physical habitudes which we encounter as we travel over 
the surface of our globe, we are able to trace the exist- 
ence of other varieties even more remarkable. The geo- 
logist has been able to turn back a few leaves of the 
earth's past history, and though the pages have been de- 
faced and mutilated by Time's unsparing hand, he is yet 
able to read in them of many strange vicissitudes to which 
the continents and oceans of our globe have been exposed. 
But, far back as he can trace the earth's history — and 
already he counts her age by millions of years — he finds 
no evidence of an epoch when life was absent from her 
surface. Nay, if he reads aright the mysterious lesson 
which the blurred letters teach him, he is led to believe 
that, at the most distant epoch to which his researches 
have extended, there was the same wonderful variety in 
the forms of life as at the present day. He can, indeed, 
find the scattered remains of only a few of those old-world 
creatures ; but he recognizes in those which have been 
preserved the clearest evidence that thousands of others 
must have existed around them. He knows that of a 
million creatures now existing scarcely one will leave to 
future ages any record of its existence ; he sees whole 
races vanishing from the earth, leaving no trace behind 
them ; and he is thus able to form an estimate of the 
enormous extent by which the creatures and races of 
which he can learn nothing must have outnumbered those 
whose scattered remains attest their former existence 
upon the earth. 



M OTHER WOULD S THAN OtJBS. 

Here, then, we have analogies which there is no mistak- 
ing. We see that not only is Nature careful to fill all 
available space with living forms, but that no time over 
which our researches extend has found her less prodigal of 
life. We see that, within very wide limits, she has a sin- 
gular power of adapting living creatures to the circum- 
stances which surround them. Nor is this lesson affected 
— like the general lesson drawn from the mere fact of the 
earth's being inhabited — by anything we can learn from 
the aspect of our satellite. For the arguments against 
the presence of living creatures on the moon are founded 
on the evidence we have that the physical habitudes of 
that orb are outside the limits within which Nature effects 
the adaptation spoken of. 

The moon teaches us, however, that all the celestial 
bodies are not at all times habitable. The sun also 
teaches the same lesson. And it is necessary that we 
should consider how far the evidence presented by our 
own earth may serve to elucidate this teaching. We shall 
see that terrestrial analogies afford a very sure guide in the 
midst of many perplexities presented by the study of the 
worlds around us. 

Let us trace out the various degrees of fitness or unfit- 
ness for the support of particular forms of life, which we 
recognize in various regions of our earth. 

Often, where there exists so slight a difference between 
two regions of the earth that, to ordinary observation, it 
would appear that the forms of life existing in one should 



WHAT OUR EARTH TEACHES US. 25 

be well adapted to the other also, we jet find that this is 
not the case. Some minute peculiarity of soil, or climate, 
or vegetation, will render one region absolutely uninhab- 
itable by a race which lives and thrives in the other. 
Darwin mentions several instances in which an apparently 
insignificant change in the circumstances under which a 
particular race has thriven, and sometimes a change which 
does not, at first sight, appear to be in the least connected 
with the well-being of the race, has led to its gradual dis- 
appearance. And it seems demonstrated that even the 
slow processes of change to which every part of the earth 
is subjected would suffice to destroy a number of the races 
now subsisting on its surface, were the characteristics of 
those races unalterable. But as the physical habitudes of 
their abode slowly change, the various races of living creat- 
ures slowly change also, so as to adapt themselves contin- 
ually to the varying circumstances under which they live. 
The lesson taught us by this peculiarity is very obvious. 
On the one hand, we see that it would be by no means 
sufficient to indicate a general resemblance between the 
physical habitudes of our earth and those of some far 
distant planet, in order to prove that that planet is the 
abode of living creatures resembling those on our own 
earth. But, on the other hand, we are taught that the 
existence of differences sufficient to render a distant planet 
an unsuitable abode for such creatures as we are familiar 
with cannot force upon us the conclusion that the planet 
is uninhabited. On the contrary, the circumstance w$ 



26 OTHER WOBLDS THAN OUBS. 

have been considering teaches us that such differences as 
would suffice to banish life of certain kinds are insufficient 
to banish life of all kinds, or even to render less abundant 
the forms of life which exist under those changed condi- 
tions. 

And now we may proceed a step further. On our earth 
we find differences of climate and physical habitudes gen- 
erally, which are much more important than those hitherto 
dealt with. We see that not only would certain races 
perish in the long run, if removed from their own abode to 
other parts of the earth, but that, in some instances, the 
process of destruction would be very rapid indeed. If we 
were to remove the polar bears from their Arctic fastnesses 
to tropical, or even to the warmer parts of temperate 
regions, a very few years would see the end of the whole 
race. The races inhabiting steppes and prairies would 
quickly perish if removed to mountain regions. Those 
accustomed to a moisture-laden air and abundant vegeta- 
tion would not survive long if removed to the desert. 

In some races, indeed, we find a power of enduring 
such changes which very far exceeds that possessed by 
other races. Those creatures, for example, which man 
has domesticated seem capable of enduring a variety of 
climate or of circumstances, which would destroy the 
seemingly more vigorous races not yet subdued to the 
yoke of man.* 

* Humboldt tells us that ' ' the pliability of the organisation of those 
animals which man has subjected to his sway enables horses, cows, and 



WHAT OUR EARTH TEACHES US. 27 

Even man himself, however, though he possesses in an 
unrivalled degree the power of enduring in safety the 
most complete change of climate, scene, and circum- 
stances, is yet limited, in a certain sense, in his power of 
migration. The Englishman, for example, can endure the 
fiercest heat of the tropics or the bitterest cold of Arctic 
and Antarctic regions. But he cannot safely attempt to 
found true colonies in every part of the earth's surface. 
Our countrymen in India must send their children to be 
reared in England, if they wish them to grow up strong 
and vigorous. There can be little doubt that if a thou- 
sand men and women from this country were to settle in 
certain parts of India (not at any time intermarrying with 
the natives), the colony would disappear within a couple 
of centuries. 

Here we have a second degree of unfitness, according 
to which certain countries would quickly become depopu- 
lated, if supplied with inhabitants from certain other 
countries. "We are taught the same lesson as before, but 
in a more striking manner. "We see that differences exist 
within the confines of our own earth which render partic- 
ular countries absolutely uninhabitable by particular races, 
insomuch that, though the individual might survive, the 



other species of European origin to lead for a time an amphibious life 
surrounded by crocodiles, water serpents, and manatees. When the 
rivers return again to their beds, the horses roam in the savannah, which 
is then spread over with a fine odoriferous grass ; and enjoy, as in their 
native climate, the renewed vegetation of spring." 



28 OTHER WORLDS THAN OURS. 

race itself would quickly perish. And we see, on the 
other hand, that these countries are not uninhabited, or 
even less fully peopled with living creatures, than seem- 
ingly more fortunate abodes. 

Now, if some impassable barrier prevented the in- 
habitants of one country from visiting others, while yet 
it was possible to learn something of the conditions pre- 
vailing in other regions, how readily the conclusion might 
be reached that some, at least, of those inaccessible regions 
must be wholly uninhabited, simply because their physical 
habitudes appeared unsuited to the wants of the only 
creatures with which the observer was familiar. Who 
would believe, for example, that men can live, and not 
only live, but thrive and multiply, in the frost-bound re- 
gions within the Arctic Circle, if travellers had not visited 
the Esquimaux races, and witnessed the conditions under 
which they subsist ? Again, if we knew nothing of India, 
and some one pictured to us the intense heat of the Indian 
sun, the strange alternations of weather which replace to 
the Indian the seasonal changes we are familiar with, and 
all the other circumstances which render tropical regions 
so different from our English home, who could believe 
that, amid those seemingly unendurable vicissitudes, 
there are races of men that thrive and multiply, even as 
our people in their temperate zone ? * 

* Perhaps the most striking instance of man's power of living under 
circumstances seemingly the most unfavorable is to be found in the fact 
that, though the strongest traveller is affected seriously by the rarity of 



WHAT OUR EARTH TEACHES US. 29 

Therefore, in examining the circumstances of other 
worlds than ours, it will not be sufficient to prove that 
certain orbs would obviously not be habitable by the 
races subsisting on the earth, in order to enforce the 
conclusion that no living creatures subsist at all upon 
their surface. 

Yet another step further, however. There are regions 
of the earth where the members of races belonging to 
other regions quickly perish. The air of our own Eng- 
land is death to many creatures. And indeed, there is 
not a spot in the whole world which would not be fatal in 
a brief space to many animals and plants belonging to 
other regions. Yet each spot, though thus fatal to certain 
races, is inhabited by numbers of others which live and 
thrive upon its surface. 

Here, then, is our third lesson. We are taught by the 
analogy of our earth that it is not even sufficient to show 
that a planet would be an abode quickly fatal to all the 
living creatures subsisting on our globe to prove that it 
is therefore uninhabited. 

But we have yet a stronger argument to touch on. 
i'here are regions of our earth to which creatures from 
other regions cannot be removed without being immedi' 



the air at great elevations, yet races of men live and thrive in Potosi, 
Bogota, and Quito, and— to use the words of a modern writer — that 
bull-fights should be possible at an elevation at which Saussure hardly 
had energy to consult his instruments, and where even his guides faint 
ed as they tried to dig a small hole in the snow. 



30 OTHER WORLDS THAN OURS. 

ately killed. The warm-blooded animal perishes if 
placed for a brief space under water. The fish perishes 
if placed for a brief space on the earth. * What could 
be more wonderful to us, were we not familiar with the 
fact, than that there are living creatures within the depths 
of that ocean beneath whose surface we ourselves, and 
the land creatures we are familiar with, cannot remain 
alive many minutes ? If fishes could reason, how could 
they believe that creatures can live in that element which 
is death to them ? Yet land and river and sea are alike 
peopled with living creatures, each race as well adapted 
as its fellows to the circumstances in which it is placed. 

We are taught, then, yet another lesson. We see that 
even though we could prove that every living creature on 
this earth would at once perish if removed to another 
orb, yet we cannot thence conclude that that orb is unin- 
habited. On the contrary, the lesson conveyed by our 
earth's analogy leads to the conclusion that many worlds 
may exist, abundantly supplied with living creatures of 
many different species, where yet every form of life upon 
our earth — bird, beast, or fish, reptile, insect, or animal- 
cule — would perish in a few moments, f 



* Perhaps the fact that there are certain kinds of fish which cannot 
only live out of water, but can travel across the dry land, or climb 
trees, affords an even more striking instance of Nature's power of 
adapting creatures to the circumstances which surround them. 

f I might add to the instances here cited many others which seem 
even more striking. We know that in strong acids which would in- 
stantly kill bird, beast, fish, or insect placed within them, there exist 



WHAT OUR EARTH TEACHES US. 31 

There remains yet a last lesson to be drawn from ter- 
restrial analogies. On the earth there are regions where 
no form of life exists or can exist. Within the flaming 
crater of the volcano, or in the frozen heart of the ice- 
berg, no living creature has its being. Yet even here 
Nature proves to us that the great end and aim of all her 
working is to afford scope and room for new forms of 
life, or to supply the wants of those which already exist. 
The volcano will die out, and the scene of its activity will 
one day become the abode of myriads of living creatures 
who would have perished in a moment in its consuming 
fires. The iceberg will melt, and its substance will once 
again be peopled with busy life. But this is little. Ii 
is the work of which volcano and iceberg are the signs, 
which most significantly teaches us what is Nature's real 
aim. The volcano is the index of those busy subterra- 
nean forces which are remodelling the earth's frame, 
slowly changing the level of the land, making continents 
of oceans and oceans of continents, preserving and vivi- 
fying all things, while all things seem to suffer a gradual 
destruction. The iceberg, too, has its work in remodel- 



and thrive minute creatures, adapted by Nature to the strange condi- 
tions in which they are placed. Even in the bowels of the earth and 
in the very neighborhood of active volcanoes, we find the volcano-fish 
existing in such countless thousands that when they are from time to 
time vomited forth by the erupting mountain their bodies are strewn 
over enormous regions, and, as they putrefy beneath the sun's rays, 
spread pestilence and disease among the inhabitants of the neighboring 
districts. 



32 OTHER WORLDS TEAN OURS. 

ling and fashioning the surface of new continents. It 
also acts an important part in the formation and mainte- 
nance of the system of oceanic circulation on which the 
welfare of land creatures and water creatures so largely 
depends. And so of a multitude of other phenomena, 
which appear at first sight significant rather of the de- 
struction than of the life-preserving character of Nature. 
The tornado and the thunder-storm, the earthquake and 
the volcano — nay, even the dreaded returns of plague and 
pestilence — have each a more powerful influence by far 
toward the preservation than they have toward the de- 
struction of life. 

"We see, then, that even if we could prove that an orb 
in space is so circumstanced that no life could by any 
possibility exist upon its surface ; if it were the scene of 
a fierce and destructive turmoil, one moment of which 
would suffice to destroy every living creature now exist- 
ing upon the earth ; if its whole mass were heated to a 
degree a thousandfold more intense than that of the 
fiercest heat we know of ; if its surface were bound in a 
cold compared with which our Arctic frosts would seem 
like tropical heat ; or even if the most rapid alternation 
of these extremes took place upon and within it — even 
then we could not conclude that it has not been in long- 
past ages, or will not be in ages yet to come, the abode 
of life. 

Lastly, even when we can safely assert of any celestial 
object that neither now, nor at any past or future time, 



WHAT OUR EARTH TEACHES ITS. 33 

could it serve as the abode of living creatures, we are led 
by terrestrial analogies to the conclusion that it yet sup- 
ports life in other ways. So that these very orbs, of 
which it seems safest to assert that they are, have ever 
been, and must ever remain uninhabited, speak to us, no 
less strongly than those which appear best suited for 
habitation, of the existence of other worlds than ours. 
% 



34 OTHER WORLDS THAN OURS. 



CHAPTER H. 

WHAT WE LEAEN FROM THE SUN. 

I do not propose to dwell in this chapter on the views 
which have been propounded respecting the sun's habita- 
bility. It is not merely that I regard those views as too 
fanciful to find place in a serious consideration of the 
subject I am dealing with, nor that the progress of recent 
observation has rendered them utterly untenable, but 
that, in fact, they do not belong to what the sun teaches 
us. I wish to consider only the real evidence which the 
sun affords respecting the scheme of creation, to dwdl 
upon the purposes which he subserves in the econoniy of 
the solar system, and thence to deduce a lesson respect- 
ing those other suns scattered through space which we 
«all the fixed stars. 

Let us first endeavor to form adequate conceptions re- 
specting the dimensions of the great central luminary of 
the solar system. 

Let the reader consider a terrestrial globe three inches 
in diameter, and search out on that globe the tiny tri- 
angular speck which represents Great Britain. Then let 
him endeavor to picture the town in which he lives as 
represented by the minutest pin-mark that could possi- 



WHAT WE LEARN FROM THE SUN. 35 

bly be made upon this speck. He will then have formed 
some conception, though but an inadequate one, of the 
enormous dimensions of the earth's globe, compared with 
the scene in which his daily life is cast. Now, on the 
same scale, the sun would be represented by a globe 
about twice the height of an ordinary sitting-room. A 
room about twenty-six feet in length, and height, and 
breadth, would be required to contain the representation 
of the sun's globe on this scale, while the globe repre- 
senting the earth could be placed in a moderately large 
goblet. 

Such is the body which sways the motions of the solar 
system. The largest of his family, the giant Jupiter, 
though of dimensions which dwarf those of the earth or 
Yenus almost to nothingness, would yet only be repre- 
sented by a thirty-two-inch globe, on the scale which 
gives to the sun the enormous volume I have spoken of. 
Saturn would have a diameter of about twenty-eight 
inches, his ring measuring about five feet in its extreme 
span. Uranus and Neptune would be little more than a 
foot in diameter, and all the minor planets would be less 
than the three-inch earth. It will thus be seen that the 
sun is a worthy centre of the great scheme he sways, 
even when we merely regard his dimensions. 

The sun outweighs fully seven hundred and thirty times 
the combined mass of all the planets which circle around 
him, so that when we regard the energy of his attraction, 
we still find him a worthy ruler of the planetary scheme. 



36 omm woblds tban oum. 

But, after all, the enormous volume and mass of the 
sun form the least important of his characteristics as the 
ruling body of the solar system. It is when we contem- 
plate him as the source whence the supplies of heat and 
light required by our own world and the other planets 
are plentifully bestowed that we see what is his chief 
office in the economy of the planetary scheme. 

Properly speaking, the physical constitution of the sun 
only requires to be dealt with in such a work as the 
present, in so far as it is directly associated with the 
sun's action upon the worlds around him, or as it may 
bear on the question of the constitution of those worlds. 
But the subject is so interesting, and it would indeed be 
so difficult to draw a line of demarcation between the 
facts which bear upon the question of other worlds and 
those which do not, that I may be permitted to enter at 
some length into a consideration of the solar orb, as mod- 
ern physical discoveries present it to our contemplation. 

The study of solar physics may be said to have com- 
menced with the discovery of the sun-spots, about two 
hundred and sixty-seven years ago. These spots were 
presently found to traverse the solar disk in such a way 
as to indicate that the sun turns upon an axis once in 
about twenty-six days. Nor will this rotation appear 
slow when we remember that it implies a motion of the 
equatorial parts of the sun's surface at a rate exceeding 
some seventy times the motion of our swiftest express 
trains. 



WHAT WE LEARN FROM THE SUN. 37 

Next came the discovery that the solar spots are not 
surface stains, but deep cavities in the solar substance. 
The changes of appearance presented by the spots as 
they traverse the solar disk, led Dr. Wilson to form this 
theory so far back as 1779 ; but, strangely enough, it is 
only in comparatively recent times that the hypothesis 
has been finally established. For even within the last 
ten years a theory was put forward which accounted 
satisfactorily for most of the changes of appearance ob- 
served in the spots, by supposing them to be due to 
solar clouds hanging suspended at a considerable eleva- 
tion above the true photosphere. 

Sir William Herschel, reasoning from terrestrial analo- 
gies, was led to look on the spot cavities as apertures 
through a double layer of clouds. He argued that were 
the solar photosphere of any other nature, it would be 
past comprehension that vast openings should form in it, 
to remain open for months before they close up again. 
Whether we consider the enormous rapidity with which 
the spots form and with which their figure changes, or 
the length of time that many of them remain visible, we 
find ourselves alike perplexed, unless we assume that the 
solar photosphere resembles a bed of clouds. Through a 
stratum of terrestrial clouds, openings may be formed 
by atmospheric disturbances, but while undisturbed the 
clouds will retain any form once impressed upon them 
for a length of time corresponding to the weeks and 
months during which the solar spots endure. 



38 OTHER WORLDS THAN OURS. 

And because the solar spots present two distinct varie- 
ties oi light, the faint penumbra and the dark umbra or 
nucleus, Herschel saw the necessity of assuming that 
there are two beds of clouds, the outer self-luminous and 
constituting the true solar photosphere, the inner reflect- 
ing the light received from the outer layer, and so shield- 
ing the real surface of the sun from the intense light and 
heat which it would otherwise receive. 

But while recent discoveries have confirmed Sir Will- 
iam Herschel's theory about the solar cloud-envelopes, 
they have by no means given countenance to his view 
that the body of the sun may possibly be cool. The 
darkness of the nucleus of a spot is found, on the con- 
trary, to give proof that in that neighborhood the sun is 
hotter, because it parts less readily with its heat. We 
shall see presently how this is. Meantime let it be no- 
ticed in passing that a close scrutiny of large solar spots 
has revealed the existence of an intensely dark spot in 
the midst of the umbra. This spot must be regarded as 
the true nucleus. 

The circumstance that the spots appear only on two 
bands of the sun's globe, corresponding to the subtropi- 
cal zones on our own earth, led the younger Herschel to 
conclusions as important as those which his father had 
formed. He reasoned, like his father, from terrestrial 
analogies. On our own earth the subtropical zones are 
the regions where the great cyclonic storms have then 
birth, and rage with their chief fury. Here, therefore, 



WHAT WE LEARN FROM TBE SUN 39 

we have tlie analogue of the solar spots, if only we can 
show reason for believing that any causes resembling 
those which generate the terrestrial cyclone operate upon 
those regions of the sun where the solar spots make their 
appearance. 

We know that the cyclone is due to the excess of heat 
at the earth's equator. It is true that this excess of heat 
is always in operation, whereas cyclones are not perpetu- 
ally raging in subtropical climates. Ordinarily, there- 
fore, the excess of heat does not cause tornadoes. Cer- 
tain aerial currents are generated, whose uniform motion 
suffices, as a rule, to adjust the conditions which the ex- 
cess of heat at the equator would otherwise tend to 
disturb. But when through any cause the uniform ac- 
tion of the aerial currents is either interfered with, 01 
is insufficient to maintain equilibrium, then cyclonic or 
whirling motions are generated in the disturbed atmos- 
phere, and propagated over a wide area of the earth's 
surface. 

Now we recognize the reason of the excess of heat at 
the earth's equator, in the fact that the sun shines more 
directly upon that part of the earth than on the zones 
which lie in higher latitudes. Can we find any reason 
for suspecting that the sun, which is not heated from 
without as the earth is,, should exhibit a similar peculiar- 
ity ? Sir John Herschel considered that we can. If the 
sun has an atmosphere extending to a considerable dis- 
tance from his surface, then there can be little doubt 



40 OTHER WORLDS THAN OURS. 

that, owing to his rotation upon his axis, this atmosphere 
would assume the figure of an oblate spheroid, and would 
be deepest over the solar equator. Here, then, more of 
the sun's heat would be retained than at the poles, where 
the atmosphere is shallowest. Thus that excess of heat 
at the solar equator which is necessary to complete the 
analogy between the sun-spots and terrestrial cyclones 
seems satisfactorily established. 

It must be remarked, however, that this reasoning, so 
far as the excess of heat at the sun's equator is concerned, 
only removes the difficulty a step. If there were indeed 
an increased depth of atmosphere over the sun's equator 
sufficient to retain the requisite excess of heat, then the 
amount of heat we receive from the sun's equatorial re- 
gions ought to be appreciably less than the amount 
emitted from the remaining portions of the solar surface. 
This is not found to be the case, so that, either there is 
no such excess of absorption, or else the solar equator 
gives out more heat, in other words, is essentially hotter, 
than the rest of the sun. But this is just the peculiarity 
of which we want the interpretation. 

It may be taken for granted, however, that there is an 
analogy between the sun-spots and terrestrial cyclonic 
storms, though as yet we are not very well able to under- 
stand its nature. 

We come next to one of the most interesting discover- 
ies ever made respecting the sun — the discovery that the 
spots increase and diminish in frequency in a periodic 



WHAT WE LEARN FROM THE 8UJST. 41 

manner. We owe this discovery to the laborious and 
systematic observations made by Herr Schwabe, of 
Dessau. In these pages any account of his work would 
be out of place. "We need only dwell upon the result, 
and upon other discoveries which have been made by 
observers who have taken up the same work. 

Schwabe found that in the course of about eleven years 
the solar spots pass through a complete cycle of changes. 
They become gradually more and more numerous up to 
a certain maximum, and then as gradually diminish. At 
length the sun's face becomes not only clear of spots, but 
a certain well-marked darkening around the border of 
his disk disappears altogether for a brief season. At this 
time the sun presents a perfectly uniform disk. Then 
gradually the spots return, become more and more 
numerous, and so the cycle of changes is run through 
again. 

The astronomers who have watched the sun from the 
Kew observatory have found that the process of change 
by which the spots sweep in a sort of " wave of in- 
crease " over the solar disk is marked by several minor 
variations. As the surface of a great sea-wave will be 
traversed by small ripples, so the gradual increase and 
diminution in the number of the solar spots is character- 
ized by minor gradations of change, which are sufficiently 
well marked to be distinctly cognizable. 

There seems every reason for believing that the peri- 
odic changes thus noticed are due to the influence of the 



4:2 OTHER WORLDS THAN OURS. 

planets upon the solar photosphere, though in what way 
that influence is exerted is not at present perfectly clear, 
Some have thought that the mere attraction of th^ 
planets tends to produce tides of some sort in the sola* 
envelopes. Then, since the height of a tide so produced 
varies as the cube or third power of the distance, it has 
been thought that a planet when in perihelion would 
generate a much larger solar tide than when in aphelion. 
So that, as Jupiter has a period nearly equal to the sun- 
spot period, it has been supposed that the attractions of 
this planet are sufficient to account for the great spot- 
period. Yenus, Mercury, the Earth, and Saturn have, in 
a similar manner, been rendered accountable for the 
shorter and less distinctly marked periods. 

Without denying that the planets may be, and prob- 
ably are, the bodies to whose influence the solar-spot 
periods are to be ascribed, I yet venture to express very 
strong doubts whether the action of Jupiter is so much 
greater in perihelion than in aphelion as to account for 
the fact that, whereas at one season the face of the sun 
shows many spots, at another it is wholly free from 
them. 

However, we are not at present concerned so much 
with the explanation of facts as with the facts themselves. 
We have to consider rather what the sun is, and what he 
does for the solar system, than why these things are so. 

Let us note, before passing to other circumstances of 
interest connected with the sun, that the variable condi- 



WHAT WE LEARN FROM TEE SUN 43 

tion of his photosphere must cause him to change in 
brilliancy as seen from vast distances. If Herr Schwabe, 
for instance, instead of observing the sun's spots from his 
watch-tower at Dessau, could have removed himself to a 
distance so enormous that the sun's disk would have been 
reduced, even in the most powerful telescope, to a mere 
point of light, there can be no doubt that the only effect 
which he would have been able to perceive would have 
been a gradual increase and diminution of brightness, 
having a period of about eleven years. 

Our sun, therefore, if viewed from the neighborhood of 
any of the stars, whence undoubtedly he would simply 
appear as one among many fixed stars, would be a " vari- 
able," having a period of about eleven years, and a very 
limited range of variation. Further, if an observer, view- 
ing the sun from so enormous a distance, had the means 
of very accurately measuring its light, he would undoubt- 
edly discover that while the chief variation of the sun 
takes place in a period of about eleven years, its light is 
subjected to minor variations, having shorter periods. 

The discovery that the periodic changes of the sun's 
appearance are associated with the periodic changes in 
the character of the earth's magnetism is the next that 
we have to consider. 

It had long been noticed that during the course of a 
single day the magnetic needle exhibits a minute change 
of direction, taking place in an oscillatory manner. And 
when the character of this vibration came to be carefully 



44 OTHER WORLDS THAN OURS. 

examined, it was found to correspond to a sort of effort 
on the needle's part to turn toward the sun. For exam- 
ple, when the sun is on the magnetic meridian, the needle 
has its mean position. This happens twice in the day, 
once when the sun is above the horizon, and once when 
he is below it. Again, when the sun is midway between 
these two positions — which also happens twice in the day 
— the needle has its mean position, because the northern 
and the southern ends make equal efforts, so to speak, to 
direct themselves toward the sun. Four times in the 
day, then, the needle has its mean position, or is directed 
toward the magnetic meridian. But when the sun is not 
in one of the four positions considered, that end of the 
needle which is nearest to him is slightly turned away 
from its mean position, toward him. The change of 
position is very minute, and only the exact methods of 
observation made use of in the present age would have 
sufficed to reveal it. There it is, however, and this mi- 
nute and seemingly unimportant peculiarity has been 
found to be full of meaning. 

Had science merely measured this minute variation, 
the work would have given striking evidence of the exact 
spirit in which men of our day deal with natural phenom- 
ena. But science was to do much more. The variations 
of this minute variation were to be inquired into ; their 
period was to be searched for ; the laws by which they 
were regulated, and by which their period might perhaps 
itself be rendered variable, were to be examined; and 



WHAT WE LEARN FROM THE SUN. 45 

finally their relation to other natural laws was to be 
sought after. That science should set herself to an in- 
quiry so delicate and so difficult, in a spirit so exacting, 
was nothing unusual. It is thus that all the great dis- 
coveries of our age have been effected. But it is well that 
the reader should recognize the careful scrutiny to which 
natural phenomena have been subjected before the great 
laws we have to consider were made known. It is 
thought by many, who have not been at the pains to 
examine what science is really doing in our day, that the 
wonders she presents to men's contemplation, the start- 
ling revelations which are being made from day to day, 
are merely dreams and fancies which replace indeed the 
dreams and fancies of old times, but have no worthier 
claims on our belief. Those who carefully examine the 
history of science will be forced to adopt a very different 
opinion. 

The minute vibrations of the magnetic needle, thus 
carefully watched — day after day, month after month, 
year after year — were found to exhibit a yet more minute 
oscillatory change. They waxed and waned within nar- 
row limits of variation, but yet in a manner there was no 
mistaking. The period of this oscillatory change was not 
to be determined, however, by the observations of a few 
years.* Between the time when the diurnal vibration 



* The reader must not understand that the account here given pre- 
sents in any sense even a general view of the labors of those who have 
studied the earth's magnetism. I touch only on those points by which 



46 OTHER WORLDS THAN 0TJR8. 

was least until it had reached its greatest extent, and 
thence returned to its first value, no less than eleven 
years elapsed, and a much longer time passed before the 
periodic character of the change was satisfactorily deter- 
mined. 

The reader will at once see what these observations 
tend to. The sun-spots vary in frequency within a period 
of eleven years, and the magnetic diurnal observations 
vary within a period of the same duration. It might 
seem fanciful to associate the two periodic series of 
changes together, and doubtless when the idea first oc- 
curred to Sabine, it was not with any great expectation 
of finding it confirmed, that he examined the evidence 
bearing on the point. Judging from known facts, we 
may see reasons for such an expectation in the corre- 
spondence of the needle's diurnal vibration, with the sun's 
apparent motion, and also in the law which associates the 
annual variations of the magnet's power with the sun's 
distance. But undoubtedly when the idea occurred to 
Sabine, it was an exceedingly bold one, and the ridicule 
with which the first announcement of the supposed law 
was received, even in scientific circles, suffices to show 
how unexpected that relation was which is now so thor- 
oughly established. For a careful comparison between 



the association between the earth's magnetism and the physical condi- 
tion of the sun are most clearly indicated ; because these points alone 
bear an the subject of this chapter. How they do so will appear fur- 
ther on. 



WHAT WE LEARN FROM THE SUN. 4? 

the two periods has demonstrated that they agree most 
perfectly, not merely in length, but maximum for maxi- 
mum, and minimum for minimum. When the sun-spots 
are most numerous, then the daily vibration of the mag- 
net is most extensive ; while when the sun's face is clear 
of spots, the needle vibrates over its smallest diurnal arc. 
Then the intensity of the magnetic action has been 
found to depend upon solar influences. The vibrations 
by which the needle indicates the progress of those strange 
disturbances of the terrestrial magnetism which are known 
as magnetic storms, have been found not merely to be 
most frequent when the sun's face is most spotted, but to 
"occur simultaneously with the appearance of signs of dis- 
turbance in the solar photosphere. For instance, during 
the autumn of 1859, the eminent solar observer, Carring- 
ton, noticed the apparition of a bright spot upon the sun's 
surface. The light of this spot was so intense that he 
imagined the screen which shaded the plate employed to 
receive the solar image had been broken. By a fortunate 
coincidence another observer, Mr. Hodgson, happened to 
be watching the sun at the same instant, and witnessed 
the same remarkable appearance. Now it was found that 
the self -registering magnetic instruments of the Kew ob« 
servatory had been sharply disturbed at the instant when 
the bright spot was seen. And afterward it was learned 
that the phenomena which indicate the progress of a 
magnetic storm had been observed in many places. Tele- 
graphic communication was interrupted, and at a station 



4:8 OTHER WORLDS THAN OURS. 

in Norway the telegraphic apparatus was set on fire ; 
auroras appeared both in the northern and southern hem- 
ispheres during the night which followed ; and the whole 
frame of the earth seemed to thrill responsively to the 
disturbance which had affected the great central lumi- 
nary of the solar system. 

The reader will now see why I have discussed relations 
which hitherto he may perhaps have thought very little 
connected with my subject. He sees that there is a bond 
of sympathy between our earth and the sun ; that no dis- 
turbance can affect the solar photosphere, without affecting 
our earth to a greater or less degree. But if our earth, 
then also the other planets. Mercury and Venus, so 
much nearer the sun than we are, surely respond even 
more swiftly and more distinctly to the solar magnetic 
influences. But beyond our earth, and beyond the orbit 
of moonless Mars, the magnetic impulses speed with the 
velocity of light. The vast globe of Jupiter is thrilled 
from pole to pole as the magnetic wave rolls in upon it ; 
then Saturn feels the shock, and then the vast distances 
beyond which lie Uranus and Neptune are swept with the 
ever-lessening yet ever- widening disturbance-wave. Who 
shall say what outer planets it then seeks ? or who, looking 
back upon the course over which it has travelled, shall say 
that planets alone have felt its effects? Meteoric and 
cometic systems have been visited by the great magnetic 
wave, and upon the dispersed members of the one and the 
subtle structure of the other effects even more important 



WHAT WE LEARN FROM THE SUN 49 

may have been produced than those striking phenomena 
which characterize the progress of terrestrial or planetary 
magnetic storms. 

When we remember that what is true of a relatively 
great solar disturbance, such as the one witnessed by 
Messrs. Carrington and Hodgson, is true also (however 
different in degree) of the magnetic influences which the 
sun is at every instant exerting, we see that a new and 
most important bond of union exists between the mem- 
bers of the solar family. The sun not only sways them 
by the vast attraction of his gravity, not only illumines 
them, not only warms them, but he pours forth on all his 
subtle yet powerful magnetic influences. A new analogy 
between the members of the solar system is thus intro- 
duced. 

And now we pass on to other discoveries, bearing at 
-once and with equal force upon the relations between the 
Various members of the solar system and upon the posi- 
tion which that system occupies in the universe. 

Hitherto we have been considering the teachings of 
the telescope ; we have now to consider what we have 
learned by means of an instrument of yet higher powers. 
As I shall have to refer very frequently, throughout this 
volume, to the teachings of the spectroscope, it will be 
well that I should briefly describe what it is that this 
instrument really effects. Were I simply to state the 
results of its use, without describing its real character, 
many of my readers would be disposed to believe that 



50 OTHER WORLDS THAN OURS. 

astronomers are as credulous as in reality they are ex- 
acting and scrupulous, where new facts and observations 
are in question. 

The real end and aim of the telescope, as applied by 
the astronomer to the examination of the celestial ob- 
jects, is to gather together the light which streams from 
each luminous point throughout space. We may regard 
the space which surrounds us on every side as an ocean 
without bounds or limits, an ocean across which there 
are ever sweeping waves of light either emitted directly 
from the various bodies subsisting throughout space, or 
else reflected from their surfaces. Other forms of wave 
also speed across those limitless depths in all directions ; 
but the light-waves are those which at present concern us. 
Our earth is as a minute island placed within the ocean 
of space, and to the shores of this tiny isle the light- 
waves bear their message from the orbs which lie like 
other isles amid the fathomless depths around us. With 
the telescope the astronomer gathers together portions of 
light-waves which else would have travelled in diverging 
directions. By thus intensifying their action, he enables 
the eye to become cognizant of their true nature. Pre- 
cisely as the narrow channels around our shores cause the 
tidal wave, which sweeps across the open ocean in almost 
insensible undulations, to rise and fall through a wide 
range of variation, so the telescope renders sensible the 
existence of light-waves which would escape the notice 
of the unaided eye. 



WHAT WE LEARN FROM THE SUN. 51 

The telescope, then, is essentially a light-gatherer. 

The spectroscope is used for another purpose. It 
might be called the light-sifter. It is applied by the as- 
tronomer to analyze the light which comes to him from 
beyond the ocean of space, and so to enable him to learn 
the character of the orbs from which that light proceeds. 

The principle of the instrument is simple, though the 
appliances by which its full powers can alone be educed 
are somewhat complicated. 

A ray of sunlight falling on a prism of glass or crystal 
does not emerge unchanged in character. Different por- 
tions of the ray are differently bent, so that when they 
emerge from the prism they no longer travel side by side 
as before. The violet part of the light is bent most, the 
red least; the various colors from violet through blue, 
green, and yellow, to red, being bent gradually less and 



The prism then sorts, or sifts, the light-waves. 

But we want the means of sifting the light-waves more 
thoroughly. The reader must bear with me while I de- 
scribe, as exactly as possible in the brief space available 
to me, the way in which the first rough work of the prism 
has been modified into the delicate and significant work 
of the spectroscope. It is well worth while to form clear 
views on this point, because so many of the wonders of 
modern science are associated with spectroscopic analysis. 

If, through a small round hole in a shutter, light is ad- 
mitted into a darkened room, and a prism be placed with 



52 OTHER WORLDS THAN OURS. 

its refracting angle downward and horizontal, a vertical 
spectrum, having its violet end uppermost, will be formed 
on a screen suitably placed to receive it. 

But now let us consider what this spectrum really is. 
If we take the light-waves corresponding to any particu- 
lar color, we know from optical considerations that these 
waves emerge from the prism in a pencil exactly resemb- 
ling in shape the pencil of white light which falls on the 
prism. They therefore form a small circular or oval 
image on their own proper part of the spectrum. Hence 
the spectrum is in reality formed of a multitude of over- 
lapping images, varying in color from violet to red. It 
thus appears as a rainbow-tinted streak, presenting every 
gradation of color between the utmost limits of visibility 
at the violet and red extremities. 

If we had a square aperture to admit the light, we 
should get a similar result. If the aperture were oblong, 
there would still be overlapping images ; but if the length 
of the oblong were horizontally-placed oblong, the over- 
lapping would be less than when the images were square. 
Suppose we diminish the overlapping as much as possi- 
ble ; in other words, suppose we make the oblong slit as 
narrow as possible. Then, unless there were in reality an 
infinite number of images distributed all along the spec- 
trum from top to bottom, the images might be so nar- 
rowed as not to overlap ; in which case, of course, there 
would be horizontal dark spaces or gaps in our spectrum. 
Or again, if we failed in finding gaps of this sort by 



WHAT WE LEARN FROM THE SUN. 53 

simply narrowing the aperture, we might lengthen the 
spectrum by increasing the refracting angle of the prism, 
or by using several prisms, and so on. 

The first great discovery in solar physics, by means of 
the analysis of the prism (though the discovery had little 
meaning at the time), consisted in the recognition of the 
fact that by means of such devices as the above, dark 
gaps or cross-lines can be seen in the solar spectrum. In 
other words, light- waves of the various gradations corre- 
sponding to all the tints of the spectrum from violet to 
red, do not travel to us from the great central luminary 
of our system. Kemembering that the effect we call 
color is due to the length of the light-waves, the effect of 
red corresponding to light-waves of the greatest length, 
while the effect of violet corresponds to the shortest light- 
wave, we see that in effect the sun sends forth to the 
worlds which circle around him light-waves of many dif- 
ferent lengths, but not of all lengths. Of so complex and 
interesting a nature is ordinary daylight. 

But spectroscopists sought to interpret these dark lines 
in the solar spectrum, and it was in carrying out this in- 
quiry — which even to themselves seemed almost hopeless, 
and to many would appear an utter waste of time — that 
they lighted upon the noblest method of research yet re- 
vealed to man. 

They examined the spectra of the light from incandes- 
cent substances (white-hot metals and the like), and 
found that in these spectra there are no dark lines. 



54 OTHER WORLDS THAN OURS. 

They examined the spectra of the light from the stars, 
and found that these spectra are crossed by dark lines re- 
sembling those in the solar spectrum, but differently ar- 
ranged. 

They tried the spectra of glowing vapors, and they 
obtained a perplexing result. Instead of a number of 
dark lines across a rainbow-tinted streak, they found 
bright lines of various color. Some gases would give a 
few such lines, others many, some only one or two. 

Then they tried the spectrum of the electric spark, and 
they found here also a series of bright lines, but not 
always the same series. The spectrum varied according 
to the substances between which the spark was taken and 
the medium through which it passed. 

Lastly, they found that the light from an incandescent 
solid or liquid, when shining through various vapors, no 
longer gives a spectrum without dark lines, but that the 
dark lines which then appear vary in position, according 
to the nature of the vapor through which the light has 
passed. 

Here were a number of strange facts, seemingly too 
discordant and too perplexing to admit of being inter- 
preted. Yet one discovery only was wanting to bring 
them all into unison. 

In 1859 Kirchhoff, while engaged in observing the solar 
spectrum, lighted on the discovery that a certain double 
dark line which had already been found to correspond 
exactly in position with the double bright line forming 



WHAT WE LEARR *isvM THE STJN. 55 

the spectrum of the glowing vapor of sodium, was inten- 
sified when the light of the sun was allowed to pass 
through that vapor. This at once suggested the idea that 
the presence of this dark line (or, rather, pair of dark lines) 
in the spectrum of the sun is due to the existence of the 
vapor of sodium in the solar atmosphere, and that this 
vapor has the power of absorbing the same order of light- 
waves as its emits. It would of course follow from this 
that the other dark lines in the solar spectrum are due to 
the presence of other absorbent vapors in its atmosphere, 
and that the identity of these would admit of being es- 
tablished in the same way, supposing this general law 
to hold that a vapor emits the same light-waves that it is 
capable of absorbing. 

Kirchhoff was soon able to confirm his views by a 
variety of experiments. The general principles to 
which his researches led — in other words, the principles 
which form the basis of spectrum analysis — are as fol- 
lows : 

1. An incandescent solid or liquid gives a continuous 
spectrum. 

2. A glowing vapor gives a spectrum of bright lines, 
each vapor having its own set of lines, so that from the 
appearance of a bright-line spectrum one can tell the 
nature of the vapor or vapors whose light forms the 
spectrum. 

3. An incandescent solid or liquid shining through 
absorbent vapors gives a rainbow-tinted spectrum crossed 



56 OTHER WORLDS THAN 0TJR8. 

by dark lines, these dark lines having the same posi* 
tion as the bright lines belonging to the spectra of the 
vapors ; so that, from the arrangement of the dark lines 
in such a spectrum, one can tell the nature of the vapoi 
or vapors which surround the source of light.* 

The application of the new method of research to the 
study of the solar spectrum quickly led to a number of 
most interesting discoveries. It was found that besides 
sodium the sun's atmosphere contains the vapors of iron, 
calcium, magnesium, chromium, and other metals. The 
dark lines corresponding to these elements appear unmis- 



* To these may be added the following laws : 

4. Light reflected from any opaque body gives the same spectrum as 
It would have given before reflection. 

5. But if the opaque body be surrounded by vapors, the dark lines 
corresponding to these vapors make their appearance in the spectrum 
with a distinctness proportioned to the extent to which the light has 
penetrated those vapors before being reflected to us. 

6. If the reflecting body be itself luminous, the spectrum belonging 
to it is superadded to the spectrum belonging to the reflected light. 

7. Glowing vapors surrounding an incandescent source of light may 
cause bright lines or dark lines to appear in the spectrum, according as 
they are more or less heated ; or they may emit just so much light as 
to make up for what they absorb, in which case there will remain no 
trace of their presence. 

8. The electric spark presents a bright-line spectrum, compounded 
of the spectra belonging to the vapors of those substances between 
which, and of those through which, the discharge takes place. Ac- 
cording to the nature of these vapors and of the discharge itself, the 
relative intensity of the component parts of the spectrum will be varia- 
ble. 

Lastly, the appearance of the spectrum belonging to any element 
will vary according to the circumstances of pressure and temperature 
under which the element may emit light. 



WHAT WE LEARN FROM THE SUN. 57 

takably in the solar spectrum. There are other metals — ■ 
such as copper and zinc — which seem to exist in the sun, 
though some of the corresponding dark lines have not 
yet been recognized. As yet it has not been proved that 
gold, silver, mercury, tin, lead, arsenic, antimony, or 
aluminium exist in the sun — though we can by no means 
conclude, nor indeed is it at all probable, that they are 
absent from his substance. The dark lines belonging to 
hydrogen are very well marked indeed in the solar spec- 
trum, and, as we shall see presently, the study of these 
lines has afforded most interesting information respect- 
ing the physical constitution of the sun. 

Now, we notice at once how importantly these re- 
searches into the sun's structure bear upon the subject 
of this treatise. It would be indeed interesting to con- 
sider the actual condition of the central orb of the plane- 
tary scheme, to picture in imagination the metallic 
oceans which exist upon his surface, the continual evap- 
oration from those oceans, the formation of metallic 
clouds, and the downpour of metallic showers upon the 
surface of the sun. But apart from such considerations, 
and viewing Kirchhoff's discoveries simply in their rela- 
tion to the subject of other worlds, we have enough to 
occupy our attention. 

If it could have been shown that, in all probability, 
the substance of the sun consists of materials wholly 
different from those which exist in this earth, the conclu- 
sion obviously to be drawn from such a discovery would 



58 OTHER WORLDS THAN OURS. 

be that the other planets also are differently constituted. 
We could not find any just reason for believing that in 
Jupiter or Mars there exist the elements with which we 
are acquainted, when we found that even the central orb 
of the planetary system exhibits no such feature of 
resemblance to the earth. But now that we know quite 
certainly that the familiar elements iron, sodium, and 
calcium exist in the sun's substance, while we are led to 
believe, with almost perfect assurance, that all the ele- 
ments we are acquainted with also exist there, we see 
at once that in all probability the other planets are 
constituted in the same way. There may of course be 
special differences. In one planet the proportionate dis- 
tribution of the elements may differ, and even differ very 
markedly from that which prevails in some other planet. 
But the general conclusion remains, that the planets are 
formed of the elements which have so long been known 
as terrestrial ; for we cannot recognize any reason for 
believing that our earth alone, of all the orbs which 
circle around the sun, resembles that great central orb 
in general constitution.* 

Now, we have in this general law a means of passing 
beyond the bounds of the solar system, and forming no 
indistinct conceptions as to the existence and character 
of worlds circling around other suns. For it will be 



* It will be seen, in the chapter on " Meteors and Comets," that this 
conclusion has a most important bearing on the views we are to form 
respecting the original formation of the planetary scheme. 



WHAT WE LEARN FROM THE SUN. 59 

seen in the chapter on the stars that these orbs, like our 
sun, contain in their substance many of the so-called 
terrestrial elements, while it may not unsafely be as- 
serted that all or nearly all those elements, and few or 
no elements unknown to us, exist in the substance of 
every single star that shines upon us from the celestial 
concave. Hence we conclude that around those suns 
also there circle orbs constituted like themselves, and 
therefore containing the elements with which we are fa- 
miliar. And the mind is immediately led to speculate 
on the uses which those elements are intended to sub- 
serve. If iron, for example, is present in some noble 
orb circling around Sirius, we speculate not unreasonably 
respecting the existence on that orb — either now, or in 
the past, or at some future time — of being capable of 
applying that metal to the useful purposes which man 
makes it subserve. The imagination suggests immedi- 
ately the existence of arts and sciences, trades and man- 
ufactures, on that distant world. We know how inti- 
mately the use of iron has been associated with the 
progress of human civilization, and though we must ever 
remain in ignorance of the actual condition of intelligent 
beings in other worlds, we are yet led, by the mere pres- 
ence of an element which is so closely related to the 
wants of man, to believe, with a new confidence, that 
for such beings those worlds must in truth have been 
fashioned. 

I would fain dwell longer on the thoughts suggested 



60 OTHER WORLDS THAN OURS. 

by the researches of Kirchhoff. Gladly, too, would I 
enter at length on an account of those interesting discov- 
eries which have been made in connection with recent 
total eclipses of the sun. The requirements of space, 
however, and some doubt as to the direct bearing of the 
last-named discoveries on the subject I have in hand, 
warn me to forbear. One point, however, remains, which 
is too intimately connected with my subject to be passed 
over. 

I refer to the sun's corona. 

It has been proved that the solar prominences consist 
of glowing vapors, hydrogen being their chief constitu- 
ent. It has been found, also, by comparing observations 
of the prominence-spectra with elaborate researches into 
the peculiarities presented by the spectrum of hydrogen 
at different pressures, that even in the very neighborhood 
of the solar photosphere these vapors probably exist at a 
pressure so moderate as to indicate that the limits of the 
sun's vaporous envelope cannot lie very far (relatively) 
from the outer solar cloud-layer. 

Now the solar corona has been seen, during total 
eclipses of the sun, to extend to a distance at least equal 
to the sun's diameter from the eclipsed orb. So that, 
assuming the corona to be a solar atmosphere, it would 
have a depth of about eight hundred and fifty thou- 
sand miles, and being also drawn toward the sun by his 
enormous attractive energy (exceeding more than twenty- 
seven times that of the earth), it could not fail to exert a 



WHAT WE LEARN FROM THE SUN. 61 

pressure on his surface exceeding many thousand-fold 
that of our air upon the earth. In fact, such an atmos- 
phere, let its outermost layers be as rare as we can con- 
ceive, would yet have its lower layers absolutely liquefied, 
if not solidified, by the enormous pressure to which 
they would be subjected. "We cannot, then, believe this 
corona to be a solar atmosphere. 

Yet it is quite impossible to dissociate the corona from 
the sun. Until 1872 some attempted to do this, and not 
only so, but to make of the zodiacal light a terrestrial 
phenomenon. But they had overlooked considerations 
which oppose themselves irresistibly to such a conclu- 
sion; and since the observation of the solar eclipse of 
December, 1871, astronomers are of one accord in re- 
garding the corona as appertaining to the sun. 

But the spectroscope has given certain very perplexing 
evidence respecting the light of the corona, and it remains 
that we should endeavor to see how that evidence bears 
on the interesting problem which the corona presents to 
our consideration. 

During the total eclipse of August, 1869, the American 
observers found that the spectrum of the corona is con- 
tinuous, but crossed by certain bright lines. If we accept 
the absence of dark lines as established by the evidence 
(which is doubtful), this result seems at first sight very 
difficult to explain. Referring to the principles of spec- 
troscopic analysis stated at pp. 55, 56, it will be seen that 
we should be led to infer that the corona consists of in- 



62 OTHER WORLDS THAN OURS. 

candescent matter surrounded by certain glowing gases. 
It is difficult to suppose that this is the real explanation 
of the phenomenon. 

Now, remembering that we have two established facts 
for our guidance — (1) the fact that the outer corona can- 
not be a solar atmosphere, and (2) the fact that it must 
be a solar appendage — I think a way may be found tow- 
ard a satisfactory explanation. 

Let it be premised that the bright lines of the coronal 
spectrum correspond in position, though not in bright- 
ness, to those seen in the spectrum of the aurora, and 
that the same lines are seen in the spectrum of the zodi- 
acal light, and in that of the phosphorescent light occa- 
sionally seen oyer the heavens at night. 

Since we have every reason to believe that the light of 
the aurora is due to electrical discharges taking place in 
the upper regions of the air, we are invited to the belief 
that the coronal light may be due to similar discharges 
taking place between the particles (of .whatever nature) 
constituting the corona. 

Now, though the appearance of an aurora is due to 
some special terrestrial action (however excited), yet the 
material substances between which the discharges take 
place must be assumed to be at all times present in the 
upper regions of the air. In all probability, they are the 
particles of those meteors which the earth is continually 
encountering. And since we know that meteor systems 
must be aggregated in far greater numbers near the sun 



WHAT WE LEARN FROM THE SUJST. 63 

than near the earth, we may regard the coronal light as 
due to electrical discharges excited by the sun's action, 
and taking place between the members of such systems. 
Besides this light, however, there must necessarily be a 
large proportion of light reflected from these meteoric 
bodies. In this way the peculiar character of the coronal 
spectrum may be readily accounted for. "We know from 
the auroral spectrum that the principal bright lines due 
to the electrical discharges would be precisely where we 
see bright lines in the coronal spectrum. But, besides 
these, there would be fainter bright lines, corresponding 
to the various elements which exist in the meteoric 
masses. These elements, we know, are the same as those 
in the substance of the sun. Thus, the bright lines would 
correspond in position with the dark lines of the solar 
spectrum. Hence, as light reflected by the meteors 
would give the ordinary solar spectrum, there would re- 
sult from the combination a continuous spectrum, on 
which the bright lines first mentioned would be seen, as 
during the American eclipse. 

What the polariscope has told us respecting the corona 
is in accordance with this view. 

In the same way the quality of the zodiacal light ad- 
mits of being perfectly accounted for, without resorting 
to the hypothesis that this phenomenon is a terrestrial 
one. 

The explanation thus put forward has at least the ad- 
vantage of being founded on well-established relations, 



64 OTHER WORLDS THAN OURS. 

We know that the auroral light is associated with the 
earth's magnetism, and that meteoric bodies are continu- 
ally failing upon the earth's atmosphere. We know also 
that the sun exerts magnetic influences a thousand-fold 
more intense than those of the earth, and that in his 
neighborhood there must be many million tinier more 
meteoric systems. 

But we have other and independent reasons, which 
must not be overlooked, for considering the corona to be 
of some such nature as I have suggested. 

Leverrier has shown that there probably exists in the 
neighborhood of the sun a family of bodies whose united 
mass suffices appreciably to affect the motions of the 
planet Mercury. It would not be safe to neglect con- 
siderations thus vouched for. 

Now, whatever opinion we form as to the exact charac- 
ter of the system of bodies pointed to by Leverrier's re- 
searches — whether we suppose that system to form a zone 
around the sun, or that (as I believe) the system is 
merely due to the aggregation of meteoric perihelia in 
the sun's neighborhood — we may be quite certain that 
during a total solar eclipse the system would become 
visible. 

In the eclipse of December, 1871, striking evidence was 
obtained respecting the corona. For Janssen was able to 
perceive the solar dark lines in the spectrum of the co- 
rona — proof unmistakable that a portion of the coronal 
light is reflected sunlight. It had been a difliculty in the 



WHAT WE LEARN FROM THE SUN 65 

meteoric theory that these solar lines had not been de- 
tected in the faint continuous spectrum of the corona. 
The meteoric theory, that is, the theory that a portion of 
the coronal light is due to light-reflecting meteors round 
the sun, accorded with all the known phenomena of the 
corona except this single peculiarity, that (as was sup- 
posed) the spectrum showed no dark lines. Now that 
the dark lines have been seen, all doubt seems finally re- 
moved. As Janssen said in the letter containing the dis- 
covery, "the atmospheric theory is disposed of (tromchee), 
and we must recognize in the corona a circumsolar phe- 
nomenon containing effects of radiation, absorption, and 
reflection of light," which it must be the business of fut- 
ure eclipse observers to analyze in detail. 

During the eclipse of July, 1878, the corona was found 
to extend to at least seven or eight millions of miles from 
the body of the sun. 

It will be seen, in the chapter on "Meteors and 
Comets," how important a bearing the meteor theory of 
ohe corona (that is, of a portion of its light) has upon 
the history of the solar system. It has been partly for 
this reason that I have here briefly considered the mat- 
ter; but there is another and a most important relation 
in which these views must be regarded. 

We know that the sun is the sole source whence light 
and heat are plentifully supplied to the worlds which 
circle around him. The question immediately suggests 
itself — Whence does the sun derive those amazing stores 



66 OTHER WORLDS THAN OURS. 

of force from whence he is continually supplying his de- 
pendent worlds? We know that, were the sun a mass of 
burning matter, he would be consumed in a few thousand 
years. We know that, were he simply a heated body, 
radiating light and heat continually into space, he would 
in like manner have exhausted all his energies in a few 
thousand years — a mere day in the history of his system. 
Whence, then, comes the enormous supply of force which 
he has afforded for millions on millions of years, and 
which he will doubtless continue to afford for at least as 
long a time as the worlds which circle around him have 
need of it — in other words, for countless ages yet to 
come? 

Now there are two ways in which the solar energies 
might be maintained. The mere contraction of the solar 
substance, Helmholtz tells us, would suffice to supply 
such enormous quantities of heat, that if the heat actually 
given out by the sun were due to this cause alone, there 
would not, in many thousands of years, -be any percepti- 
ble diminution of the sun's diameter. Secondly, the con- 
tinual downfall of meteors upon the sun would cause an 
emission of heat. But though the sun's increase of mass 
from this cause would not be rendered perceptible in 
thousands of years, either by any change in his apparent 
size or by changes in the motions of his family of worlds, 
yet the supply of heat obtainable in this way can be but 
small compared with the sun's emission of heat. This 
follows from the limits between which Leverrier has 



WHAT WE LEARN FROM THE SUN. 67 

shown that the total mass of the meteors of our system 
must certainly lie.* 

It seems far from unlikely that both these processes 
are in operation at the same time. Certainly the latter 
is, for we know, from the motions of the meteoric bodies 
which reach the earth, that myriads of these bodies must 
continually fall upon the sun. If the corona and zodiacal 
light are really due to the existence of nights of meteoric 
systems circling around the sun, or to the existence in his 
neighborhood of the perihelia of many meteoric systems, 
then there must be a supply of light and heat from this 
source, though not nearly sufficient to account for the 
solar emission. 

It is worthy of notice, however, that the association 
between meteors and comets has some bearing on this 
question. We know that the most remarkable character- 
istic of comets is the enormous diffusion of their sub- 
stance. Now in this diffusion there resides an enormous 
fund of force. The contraction of a large comet to dimen- 
sions corresponding to a very moderate mean density 
would be accompanied by the emission of much heat. 
The question is worth inquiring into, whether we can in- 

* Undue stress has been laid upon the probable change in the length 
of the year, owing to the downfall of meteors upon the sun's mass. It 
is forgotten that the crowded meteors forming the solar corona are 
already within the earth's orbit, and therefore already produce their 
full effect on the length of the year. The subsidence of all these bodies 
at once upon the sun would not effect the length of the year, though it 
would lead to certain modifications in the secular perturbations of the 
-earth's orbit in figure and position. 



63 OTHER WORLDS THAN OURS. 

deed assume that all meteors which reach our atmosphere 
are solid bodies. Some may be of cometic diffusion. 
But, be this as it may, it is certain that a large portion of 
the substance of every comet is in a singularly diffused 
state. Since the meteoric systems circling in countless 
millions round the sun are, in all probability, associated 
in the most intimate manner with comets, we may recog- 
nize in this diffusion, as well as in the mere downfall of 
meteors, the source of an enormous supply of light and 
heat. 

Lastly, turning from our sun to the other suns, which 
shine in uncounted myriads throughout space, we see the 
same processes at work upon them all. Each star-sun has 
its coronal and its zodiacal disks, formed by meteoric and 
cometic systems ; for otherwise each would quickly cease 
to be a sun. Each star-sun emits, no doubt, the same 
magnetic influences which give to the zodiacal light and 
to the solar corona their peculiar characteristics. Thus 
the worlds which circle round those orbs may resemble 
our own in all those relations which we refer to terrestrial 
magnetism, as well as in the circumstance that on them 
also there must be, as on our own earth, a continual down- 
fall of minute meteors. In those worlds, perchance, the 
magnetic compass directs the traveller over desert wastes 
or trackless oceans ; in their skies, the aurora displays its 
brilliant streamers ; while, amid the constellations which 
deck their heavens, meteors sweep suddenly into view, and 
comets extend their vast length athwart the celestial vault. 



THE INFERIOR PLANETS. 69 



CHAPTEE HI. 



THE INFERIOR PLANETS. 



In considering the habitabilit y of various portions of 
the solar system, we have to draw a marked distinction 
between the planets which travel within the orbit of the 
earth and those which lie beyond its range. So far, in- 
deed, as our belief in these orbs being inhabited is con- 
cerned, we may apply the same processes of reasoning to 
one set of planets as to the other. Until it has been 
demonstrated that no form of life can exist upon a planet, 
the presumption must be that the planet is inhabited. 
But it is impossible to contemplate the various members 
of our solar system without being led to consider their 
physical habitudes rather with relation to the wants of 
such creatures as exist upon our own earth, than merely 
with reference to the existence of life of some sort upon 
their surface. Viewing Venus and Mercury in this way, 
we have a different set of relations to deal with than we 
find among the outer planets. We are struck at once with 
the marked effects which seem associable with their com- 
parative proximity to the sun's orb. This feature and the 
shortness of their period of revolution — that is, of their 



70 OTHER WORLDS THAIS' OURS. 

year — are the characteristic peculiarities we have to deal 
with. 

I would willingly pay some attention here to the story 
of Vulcan, the planet which has been supposed to circle 
yet more closely than Mercury around the centre of our 
system, were it not that I regard the existence of this 
planet as utterly unlikely. 

Mercury circles around the sun in the brief period of 
eighty-eight days, or rather less than three of our months. 
So that, if the planet has seasons, these must be sever- 
ally about three weeks long. His distance from the sun 
varies between somewhat wide limits, owing to the ec- 
centricity of his orbit. When he is nearest to the sun, he 
receives ten and a half times more light and heat from 
that luminary than we do ; but when he removes to his 
greatest distance, the light and heat he receives are re- 
duced by more than one-half. Even then, however, the 
sun blazes in the skies of Mercury with a disk four and a 
half times larger than that which he presents to the ob- 
server on earth. 

Undoubtedly these peculiarities, the shortness of the 
Mercurial year, and the immense amount of light and 
heat poured by the sun upon the planet, are circum- 
stances which do not encourage, at first sight, the belief 
that any creatures can subsist upon this planet resem- 
bling those with which we are familiar. We see at once 
that all forms of vegetation in Mercury must differ in a 
very striking manner from those which exist upon the 



THE iNFfifilOR PLANETS. 71 

earth, because their structure has to be adapted to much 
more rapid changes of temperature. And the existence 
of a totally distinct flora suggests at once the belief that 
animal life on Mercury must be very different from what 
we see around us. 

Let us, however, proceed a few steps farther. 

It has been found that Mercury rotates upon his axis, 
and if we may put faith in the observations of Schroter, 
the Mercurial day is only a few minutes longer than our 
own. But though the fact of the planet's rotation has 
been observed, it has not been found possible to deter- 
mine in what position the axis of rotation lies. It has 
been said that the planet's equator is much more inclined 
than the earth's to the plane in which the planet travels ; 
but little reliance can be placed on the evidence which 
has been adduced in favor of this view. 

We are thus left altogether in doubt as to the nature 
of the Mercurial seasons. That the planet has seasons of 
some sort we are certain, because even if the axis were so 
placed that perpetual spring reigned upon the planet — I 
mean, that the days and nights were at all times and in 
all places equal — yet his varying distance from the sun 
would give changes of temperature quite as marked as 
those which characterize our seasons in England, and 
very much more marked than those known in tropical 
regions. Of course, if this is the actual arrangement, 
there are different climates in different parts of the 
planet. Near his poles the sun, though visible for half 



72 OTHER WORLDS THAN OURS. 

the Mercurial day, attains yet but a low elevation above 
the horizon ; just as he does on a spring day within our 
own polar circles. At the equator the sun passes day 
after day to the zenith, and pours down upon the planet 
an amount of light and heat far exceeding the light and 
heat of our tropical climates. A sun immediately over- 
head, and showing a diameter varying from more than 
twice to more than three times that of our sun, must be 
a noble and may be a terrible phenomenon in the skies 
of Mercury. 

There is yet another arrangement by which, to a por- 
tion of the planet, at any rate, the Mercurial seasons 
might be tempered. If his axis is so placed that what 
would be the winter season were his orbit not eccentric 
takes place, for one hemisphere, when the planet is near- 
est to the sun, then undoubtedly it may very well happen 
(the inclination of his axis being suitably adjusted) that 
this so-called winter season is the warmest part of the 
year for that hemisphere. In this case there would be 
the least possible violence in the succession of the Mer- 
curial seasons for that hemisphere. But in the other 
hemisphere the seasonal changes would be correspond- 
ingly intensified. 

In either of these cases, it is readily conceivable that 
even forms of life resembling those we are acquainted 
with on earth might exist on Mercury, and this without 
any special provision for tempering the great heat and 
light of the sun. Those regions which correspond to our 



THE INFERIOR PLANETS. 73 

* 

temperate and tropical zones would indeed scarcely be 
habitable ; but the polar regions of the planet would not 
form a disagreeable abode. 

If, however, the equator of the planet is very much in- 
clined to the plane in which Mercury travels, it cannot 
be doubted that no form of life known upon earth can 
possibly exist upon Mercury, without some special ar- 
rangements for tempering the seasonal changes. This 
will appear when we come to deal with the effect of the 
great inclination which some astronomers have ascribed 
to the equator of Venus ; and therefore we need not con- 
sider the relation with regard to Mercury, respecting 
whose axial inclination no trustworthy information has 
hitherto been obtained. 

It remains for us to consider what sort of provision 
may have been made to temper the great heat poured by 
the sun upon Mercury. 

The climate of a planet, considered generally, is largely 
influenced by the nature of the planet's atmosphere. We 
have very clear evidence on this point, in the effects 
which we notice on our own earth. If we ascend to the 
summit of a lofty mountain, we find the air much colder 
than at its base. In India, though the full heat of a 
tropical sun is poured day after day upon the snowy 
summits of the Himalayas, yet the air continues coider 
than in the bitterest midwinter weather experienced by 
us in England. Not that the solar rays have no power. 
The heat is ? in reality, even greater than on the plains, 



74 OTHER WORLDS THAN OURS. 

because it has not been intercepted by vapor-laden air. 
But the air itself is not heated. Owing to its extreme 
rarity and dryness, it neither impedes the passage of the 
sun's heat to the earth, nor prevents the return of that 
heat from the earth by radiation or reflection ; and this 
very fact, that it does not impede the passage of heat, 
means nothing else than that the air does not become 
heated.* 

We have, then, so far as a rare atmosphere is con- 
cerned, two points to dwell upon — the readiness with 
which such an atmosphere permits the sun's heat to 
reach the surface of a planet, and the readiness with 
which it permits the planet's heat to pass away into 
space. Now we might feel doubtful which of these two 
effects was chiefly to be regarded, were it not that on our 
own earth we have experience of the effects of a very rare 
atmosphere. We know that the climate of very elevated 
regions is relatively much cooler than that of places on 
the plain. Thus we learn that the direct heating powers 

* The following passage, quoted by Professor Tyndall from Hooker's 
*' Himalayan Journals," illustrates the peculiarities referred to above : 
" At 10,000 feet, in December, at 9 a.m., I saw the mercury mount to 
132°, while the temperature of shaded snow hardly was 22°. At 13,100 
feet, in January, at 9 A.M., it has stood at 98°, with a difference of 
68. 2 \ and at 10 a.m., at 114°, with a difference of 81.4°, while the 
radiating thermometer on the snow had fallen at sunrise to 0.7°." Such 
observations as these are well worth studying. It is interesting to con- 
sider that at the summit of the highest peaks of the Himalayas the mid- 
day heat due to the sun must sometimes be near, if not above, the boil- 
ing-point corresponding to those places, since water would boil on 
Mount Everest at a temperature of little more than 160°. 



THE INFERIOR PLANETS. 75 

of the sun are not so much to be considered, in judging 
of the climate of any region, as the quality of the atmos- 
phere. 

Yet we must not deceive ourselves by inferring that 
mere rarity of atmosphere can compensate fully for an in- 
creased intensity of solar heat. It is not true that the 
climate of a place on the slopes of the Andes or the 
Himalayas corresponds to that of a region on the plain 
which has an atmosphere equally warm. The circum- 
stances are, in fact, wholly different. On the plain there 
is, it is true, the same amount of heat in the case sup- 
posed ; but the air is denser and more moisture-laden : 
the nights are warmer because the skies are less clear 
and the heat escaping from the earth is intercepted by 
clouds or by the transparent aqueous vapor in the air; 
and, lastly, there is not so great a contrast between the 
warmth of the air and the direct heat of the solar rays. 

If the atmosphere of Mercury, therefore, be excessively 
rare, as some have supposed, so as to afford an Alpine or 
Himalayan climate in comparison with the tremendous 
heat we should otherwise ascribe to the climate of the 
planet, there would by no means result a state of things 
resembling that with which we are familiar on earth. 
We must not, in our anxiety to people Mercury with 
creatures such as we know of, blind ourselves to the dif- 
ficulties which have to be encountered. We cannot thin 
the Mercurial air, without adding to the direct effects of 
the sun upon the Mercurial inhabitants. Whether in 



76 OTHER WORLDS THAN OURS. 

this way we increase the habitability of the planet may 
be doubted, when we consider that the direct action of 
the sun's rays upon the tropical regions of Mercury, thus 
deprived of atmospheric protection, would produce a 
heat four or five times greater than that of boiling water. 
It will hardly be thought that the intense cold in the 
shade, or during the Mercurial night, would compensate 
for so terrible a heat. In fact, this view of the Mercurial 
climate would lead us to find a close resemblance be- 
tween the inhabitants of the planet and the unfortu- 
nates described by Dante as doomed 

A sofferir tormenti e caldi e gieli. 

It would seem hard to believe in the existence of any 
organized forms under such conditions, unless perhaps 
such " microscopic creatures, with siliceous coverings," as 
Whewell proposed to people Venus with. 

However, we have yet to consider whether an atmos- 
phere of a different sort might not be better suited to the 
requirements of Mercury. We have seen the effects of a 
rare atmosphere ; let us inquire into those which might 
be ascribed to a dense one. 

The ordinary effect of a dense atmosphere we know to 
be an increase of heat, which is certainly not what we re- 
quire in the case of Mercury. Nor are we familiar with 
any region upon our earth in which a dense atmosphere 
produces a contrary climatic effect ; so that we have no 
analogy to support us in. the belief that possibly a dense 



THE INFERIOR PLANETS. 77 

atmosphere might, under particular circumstances, serve 
to guard a planet from the solar rays. It seems possi- 
ble, however, that an atmosphere might be so constitut- 
ed as to remain almost constantly loaded with heavy 
cloud-masses. In this case it by no means follows that 
such effects would follow as we ordinarily associate with 
a moisture-laden atmosphere. Up to a certain point, 
doubtless, the increase of moisture in the air tends to an 
increase of warmth; because the aqueous vapor exercises 
a greater effect in preventing the escape of heat from the 
earth than in guarding the earth from the solar rays. 
And, as I have said, the only climatic effect we can asso- 
ciate with the frequent presence of large quantities of 
aqueous vapor in the air, or therefore with an ordinarily 
clouded state of the sky, is that of a general increase of 
heat. But, just as we know that a cloudy day is not nec- 
essarily nor even commonly a warm day, it may well be 
that an atmosphere so dense as to be at all times cloud- 
laden serves as a protection from the sun's intense heat. 
So that, instead of assigning dense atmospheres exclu- 
sively to the more distant planets, as some astronomers 
have done, we might be led to see in an envelope of great 
density the means of defending the inhabitants of Mer- 
cury and Yenus from the otherwise unendurable rays of 
their near neighbor the sun. 

Although Mercury is not a planet which can be satis- 
factorily examined with the telescope, yet, so far as can be 
judged from his aspect, his atmosphere is in reality much 



78 OTHER WORLDS THAN OURS. 

denser than our earth's, and loaded with cloud-masses oi 
enormous extent. Still the evidence on these points is 
far from satisfactory ; and there is one peculiarity of the 
planet which does not accord with this view of the consti- 
tution of his atmosphere. Undoubtedly, if the light we 
receive from Mercury came from a cloudy envelope, it 
would be more brilliant than the light we should receive 
from the surface of continents and oceans. In fact, the 
most brilliant light we could receive from a globe of a 
given size, placed at a given distance from the sun, would 
be that which would be reflected were such a globe cov- 
ered with clouds. Now there can be no doubt whatever 
that Mercury does not reflect the same proportion of 
light from his surface that some of the planets do. He 
would be, when favorably situated, the brightest of all 
the planets, were this so ; * though, seen as he always is, 

* Placing Mercury in perihelion and at his elongation, we get a half 
disk, the planet about 90,000,000 miles from us, and about 30,000,000 
from the sun, his diameter about 3,000 miles. Now, if we wish to com- 
pare the light he then sends us with that of Jupiter at his brightest, on 
the assumption of equal reflective powers, we must take Jupiter at a 
distance of about 360,000,000 miles from us, and about 450,000,000 
miles from the sun, showing a full disk, his diameter about 90,000 
miles (I put all the numbers round for convenience of calculation). 
We find, then, that the ratio of Mercury's light to Jupiter's is 

1 (3,000)* (90,000) 2 

"2 (90,000,000) 2 x (30,000,000) 2 : (360,000,000) 2 x (450,000,000)* 

or, 
I (4) 5 (15) 2 : (30) 2 , or exactly 2 to 1. 
The observation above cited is sufficient to prove that a very different 
state of things actually prevails ; in other words, that the reflective 
powers of the two planets are very different : unless* indeed, Jupiter 
shines in part by inherent light 



THE INFERIOR PLANETS. 79 

on the bright background of a full twilight sky, he would 
not make so striking an appearance as Jupiter does, 
when in opposition. This, however, is not the case. I 
remember being much struck by the superior light of 
Jupiter, on the afternoon of February 23, 1868, when the 
two planets were very close together, Mercury being 
nearly at his brightest, whereas Jupiter, then near con- 
junction, was considerably less bright than when in op- 
position. Yenus was close by, and outshone both Mer- 
cury and Jupiter. 

It seems difficult, therefore, to believe that the light of 
Mercury comes from a cloudy envelope. But there is 
still one supposition which may restore our belief in the 
habitability of the planet by creatures not very different 
from those which inhabit our earth. If it has a double 
cloud envelope, the upper like our cirrus clouds, less com- 
pact than the lower, and permitting a portion of the sun- 
light to pass through, it is possible that the lower cloud- 
layer would be seen partly in shadow. I must admit that 
the explanation is not quite satisfactory, because, just as 
much light as the outer clouds intercepted they would 
reflect ; still, it is conceivable that the usual arrangement 
of these clouds may be such that to us, who do not look 
at the planet in the direction in which the sun's rays fall, 
but somewhat aslant, the shadows of the upper clouds 
upon the dense and compact lower envelope may be ren- 
dered in large part visible. 

After all, the reader may prefer the view whicja r,ecog- 



80 OTHER WORLDS THAN OURS. 

nizes in the polar regions of Mercury places suitable for 
organic existences, while the equatorial and neighboring 
regions are zones of fire, whose dangers the bravest Mer- 
curials, the very Livingstones upon that planet, would not 
dare to face. We may picture to ourselves, on this view, 
the various contrivances by which the inhabitants of the 
two polar (that is, in reality, temperate) circles manage to 
communicate. There may be regions where favoring cir- 
cumstances narrow the uninhabitable zone so much that 
the inhabitants of one polar circle may travel to the other 
(or, at least, cross the most dangerous portion of the hot 
zone) in the course of the Mercurial night. Or perhaps 
tunnels may be run, or sheltered cuttings made, along 
which the voyage may be made in comparative safety. 
Ocean communications there can be none, if the Mercu- 
rial skies are clear, since the sun's heat on the tropical 
zone would suffice to boil away any water which might 
find its way there. 

Certainly, the smallness of the planet and the dimin- 
ished effects of gravity upon its surface, would tend to 
make communication much easier, and the construction of 
protective tunnels or cuttings a comparatively light task. 
What the exact force of gravity at the surface of Mercury 
may be we do not know, because our means of determin- 
ing the mass of the planet are not so satisfactory as in 
the case of the other primary members of the solar sys- 
tem. If Mercury had a satellite, we could tell his weight 
at once. If he were as large as Yenus, we could tell his 



THE INFERIOR PLANETS. 81 

weight by observing his effect in disturbing the motions 
of that planet. As it is, the only means we have of 
weighing Mercury is the observation of his effect in dis- 
turbing any comet which may pass near him. In this 
way the planet has been weighed, but the balance thus 
employed is not a satisfactory one altogether, because we 
are not quite certain how much of the disturbance of a 
comet when near Mercury is due to the planet's attrac- 
tion. Formerly it was supposed that the mean density of 
Mercury is equal to that of lead ; but from the perturba- 
tions of Encke's comet in Mercury's neighborhood, astron- 
omers have been led to the conclusion that the density of 
the planet is not more than one-sixth greater than our 
earth's. It follows that as his diameter is little more 
than 3,000 miles, our earth is about fifteen times as heavy 
as Mercury. Gravity at his surface is such that a pound 
weight of ours would weigh rather less than seven ounces 
of Mercury. Hence the creatures which seem to us most 
unwieldy — the elephant, the hippopotamus, and the 
rhinoceros, or even those vast monsters, the mammoth, 
the mastodon, and the megatherium, which bore sway 
over our globe in far-off eras — might emulate on Mercury 
the agility of the antelope or the greyhound. 

There can be no doubt that where gravity acts so 
feebly, all engineering operations would be rendered very 
much simpler — bridges could have a wider span, and yet 
be stronger than our terrestrial ones, buildings could be 
loftier and yet be raised more easily, and transit of all 



82 OTHER WORLDS THAN OURS. 

sorts would be effected much more readily, while at the 
same time the distances to be traversed are very much 
less than on our earth, since the surface of Mercury is 
-tittle more than one-seventh of the earth's. 

The peculiarities which characterize Venus are for the 
most part similar in kind to those we have had to con- 
sider in the case of Mercury. But at the outset of our 
inquiries into the physical habitudes of this most beau- 
tiful planet, we must point to the striking resemblance 
which it bears, in some respects, to our own earth. So 
far, indeed, as telescopic and physical researches have yet 
led us, the planet Mars, as we shall presently see, appears 
to exhibit habitudes more closely corresponding to those 
we are apt to consider essential to the wants of living 
creatures. But in size, in situation, and in density, in 
the length of her seasons and of her rotation, in the fig- 
ure of her orbit, and in the amount of light and heat she 
receives from the sun, Yenus bears a more striking re- 
semblance to the earth than any orb within the solar sys- 
tem. In fact there is no other pair of planets between 
which so many analogies can be traced as between Yenus 
and the earth. Uranus and Neptune are similar in many 
respects, but they differ in at least as many. Jupiter and 
Saturn are, in a sense, the brother giants of the solar 
scheme, while the dwarf orbs Mars and Mercury present 
many striking points of similarity ; but between neither 
of these pairs can we trace so many features of resem- 
blance as those which characterize the twin planets Yenus 



THE INFERIOR PLANETS. 83 

and Terra, while the features of dissimilarity in either 
pair are perhaps even more obvious than the points of re- 
semblance. Had Venus but a moon as the earth has, we 
might doubt whether, in the whole universe, two orbs 
exist which are so strikingly similar to each other. 

And here we may pause for a moment to consider one 
of the most perplexing enigmas that has ever been pre- 
sented to astronomers. Are we indeed certain that 
Yenus has no moon ? The question seems a strange one, 
when it is remembered that year after year Yenus has 
been examined by the most eminent modern observers, 
armed with telescopes of the most exquisite denning 
power, without any trace of a companion orb being 
noticed. Nor indeed can any reasonable doubts be 
entertained respecting the moonless condition of Yenus 
by those who appreciate the character of modem tele- 
scopic observations. And yet, if I had begun this para- 
graph by stating the evidence in favor of the existence of 
a satellite, I believe that nearly every reader would have 
come to the conclusion that most certainly the Planet 
of Love has an attendant orb. They are not amateur 
observers only who have seen a moon attending on 
Yenus, but such astronomers as Cassini and Short, the 
latter with two different telescopes and four different 
eye-pieces. Four times, between May 3 and 11, 1761, 
Montaigne saw a body near Yenus which presented a 
phase similar to that of the planet, precisely as a satel- 
lite would have done. From these observations M. Bau- 



84 OTHER WORLDS THAN OURS. 

douin deduced for the new star a diameter of about two 
thousand miles, and a distance from Venus nearly equal 
to that which separates the moon from the earth. In 
March, 1764, again, Bodkier saw the enigmatical compan- 
ion ; Horrebow saw it a few days later ; and Montbaron 
saw it in varying . positions on March 15, 28, and 29. 
Lastly, Scheuten, who witnessed the transit of Yenus in 
1761, declares that he saw a satellite accompany Yenus 
across the face of the sun. So that we cannot be greatly 
surprised that some are still disposed to believe in the 
existence of a satellite of Yenus. 

There is little occasion to dwell upon Yenus's moon- 
less condition, because the inferior planets are much less 
affected by the want of a moon than a superior planet 
would be. The service rendered by our own moon, as a 
luminary of the night, is the least important work she 
does in our behalf. It is as the chief regulator of the 
tides that the moon befriends us most usefully. Now 
Yenus has no need of lunar tides. Assuming that she 
has oceans such as those which exist upon the earth, her 
solar tides must be about two and a half times as high 
as the solar tides raised in our own oceans. Now, since 
our lunar tidal wave is about two and a half times as 
high as the solar one, we have tides ranging between the 
highest spring tides, which are three and a half times as 
high as the solar tide alone, and the lowest neap tides, 
which are only one and a half times as high as the solar 
wave. Yenus has constant tides, therefore, correspond- 



THE INFERIOR PLANETS. 85 

ing very closely to the mean tides on our own earth; 
and therefore perfectly well adapted to subserve all the 
purposes which our tides render us, only with less va- 
riety in their mode of operation. Mercury also has 
sufficiently high solar tides, supposing he has extensive 
oceans (which may reasonably be questioned), since the 
smallness of his dimensions (tending of course to dimin- 
ish the difference of action, on which the sun's tidal 
influence depends) is fully compensated by his great 
proximity to that orb. 

Yenus has a year of 224 days 17 hours, very nearly, 
and her distance from the sun, which varies little during 
the course of a year, is somewhat less than three-fourths 
of that which separates the sun from us. Her day is 
about thirty-five minutes shorter than ours, and her 
globe somewhat smaller than the earth's. 

It is clear that, merely in the greater proximity of 
Venus to the sun, there is little to render at least a large 
proportion of her surface uninhabitable by such beings 
as exist upon our earth. The sun, as seen in her skies, 
has a diameter one-third larger than he presents to us ; 
and his apparent surface dimensions, on which of course 
his heating and illuminating powers depend, are greater 
in the proportion of about sixteen to nine. This un- 
doubtedly would render his heat almost unbearable in 
the equatorial regions of Yenus, but in her temperate 
and subarctic regions a climate which we should find 
well suited to our requirements might very well exist ; 



86 OTHER WORLDS THAN OUMS. 

while her polar regions might correspond to our temper- 
ate zones, and be the abode of the most active and enter- 
prising races existing upon her surface. 

Here, however, we have been supposing that Venus 
has seasons resembling our own in character — in other 
words, that her axis of rotation is inclined at about the 
same angle to the plane in which she travels. Observa- 
tions have been made, according to which a very different 
state of things would appear to prevail. It has been 
said, on the authority of observers of some eminence, 
that her axis in inclined only 15° to the plane of her 
orbit. * If this is really the case, a number of singular 
and somewhat complicated relations are presented, the 
result of which it may be interesting to exhibit to the 
reader. 

In the first place, the arctic regions of Venus extend 
within fifteen degrees of her equator (if the axis is really 
bowed as supposed), while the tropics extend within fif- 
teen degrees of her poles — so that two zones, larger by 
far than the temperate zones of our earth, belong both to 
her arctic and to her tropical regions. It is difficult to 
say whether her equatorial, her polar, or her arctico-trop- 
ical regions would be, to our ideas, the least pleasing por- 
tion of her globe. 

An inhabitant of the regions near either pole has to 

* If the observations of De Vico may be trusted, the inclination of 
Venus, though less than 75°, is still so considerable (about 55°) as to 
justify the general conclusions deduced in the following paragraphs. 



THE INFERIOR PLANETS. 87 

endure extremes of heat and cold such as would suffice 
to destroy nearly every race of living beings subsisting 
upon the earth. During the summer the sun circles con- 
tinually close to the point overhead, so that, day after 
day, he pours down his rays with an intensity of heat 
and of light exceeding nearly twofold the midday light 
and heat of our own tropical sun. Only for a short time, 
in autumn and in spring, does the sun rise and set in 
these regions. A spring or autumn day, like one of our 
days at those seasons, lasts about twelve hours ; but the 
sun attains at noon, in spring or autumn, a height of 
only a few degrees above the horizon. Then presently 
comes on the terrible winter, lasting about three of our 
months, but far more striking in its characteristics even 
than the long winter night of our polar regions. For, 
near our poles, the sun approaches the horizon at the 
hour corresponding to noon ; and though he does not 
show his face, he yet lights up the southern skies with a 
cheering twilight glow. But during the greater part of 
the long night of Yenus's polar regions, the sun does not 
approach within many degrees of the horizon. Nay, he 
is further below the horizon than the midnight winter 
sun of our arctic regions. Thus, unless the skies are lit 
up with auroral splendors, an intense darkness prevails 
during the polar winter which must add largely to the 
horrors of that terrible season. Certainly, none of the 
human races upon our earth could bear the alternations 
between these more than polar terrors, and an intensity 



88 OTHER WORLDS THAN OURS. 

of summer heat far exceeding any with which we are 
familiar on earth. 

Let us see whether the equatorial regions are more 
pleasing abodes. 

In these parts of Yenus there are two summers, corre- 
sponding to the spring and autumn of the polar regions. 
At these seasons the sun rises day after day to the point 
overhead, and the weather corresponds for awhile to that 
which prevails in the tropical regions of our own earth. 
But between these seasons the sun passes away alter- 
nately to the northern and southern skies. During the 
season corresponding to summer he is above the horizon 
nearly throughout the twenty-three hours of Venus's 
day ; * but he attains no great elevation, travelling always 
in a small circle close around the northern pole. During 
the season corresponding to winter he is above the hori- 
zon only a very short time each day, and is always close 
to the south, attaining only an elevation of a few de- 
grees at noon. Thus we have the following curious suc- 
cession of seasons : at the vernal equinox a summer much 
warmer than our tropical summers; about fifty-six days 
later, or at the summer solstice, weather resembling 
somewhat the spring of our temperate zones, only that 
the night is exceedingly short; yet fifty-six days later 
there is another summer, as terrible as the former ; and 



* On the equator itself, as on our own, the day is always equal in 
length to the night. The above account corresponds to a place near 
the borders of the equatorial zone. 



THE INFERIOR PLANETS. 89 

lastly, at the winter solstice, the days are shorter and the 
oold probably more intense than in the winter of places 
near our Arctic Circles. In such regions the contrasts, 
rather than either of the extremes of climate, would be 
most trying to terrestrial races; and it is scarcely toe 
much to say that no races subsisting upon our earth 
could possibly endure such remarkable changes, succeed- 
ing each other so rapidly. 

Lastly, the beings who inhabit the wide zones which 
are at once tropical and arctic have climates ranging 
between the two limits just considered. If they are neat 
the equatorial regions they suffer from all the vicissitudes 
of the equatorial climate, with this further tribulation, 
that in midwinter they do not see the sun even at mid- 
day — a circumstance by no means compensated (accord- 
ing to our ideas) by the fact that near the summer sol- 
stice the sun does not set. If they are near the polar 
regions, they have a summer even more terrible than the 
polar summer, and a winter scarcely less dreary and bitter. 

Fortunately for our belief in the habitability of Yenus, 
astronomers are far from accepting with confidence the 
assertions of those observers who have assigned to Yenus 
an inclination so remarkable. If her inclination at all 
resembles the earth's, there is every reason to believe 
that her physical habitudes also resemble those of the 
earth. In this case, the argument from analogy pre- 
sented in the opening chapter of this work, seems to 
force upon us the conclusion that she is inhabited ; while 



90 OTHER WORLDS THAN OURS. 

we may believe, though perhaps with less confidence, that 
a close resemblance subsists between the creatures which 
people her surface and those with which we are acquainted. 

We have no direct evidence, indeed, on which to ground 
our belief that the great proximity of Yenus to the sun 
may not be accompanied by any very remarkable pecu- 
liarities in the characteristics of her climate. But we 
have an indirect argument of some strength. If Yenus is 
much nearer than the earth to the sun, the earth, in turn, 
is much nearer to the sun than Mars is. Yet, as we shall 
see in the next chapter, we have clear evidence from tel- 
escopic observation, and still clearer evidence in the re- 
sults of spectroscopic research, that the climatic arrange- 
ments on Mars do not differ in any remarkable degree 
from those of our own earth. It would follow, therefore, 
as at least probable, that a similar resemblance prevails 
between the climate of the earth and that of Yenus. So 
that, despite the claim which Dr. Whewell has put in 
for microscopic animalcules with siliceous coverings as 
the sole inhabitants of Yenus, I can find no reason (if the 
abnormal axial inclination above considered is once dis- 
proved) for denying that she may be the abode of creat- 
ures as far advanced in the scale of creation as any which 
exist upon the earth. 

Gravity at the surface of Yenus is so nearly equal to 
terrestrial gravity that the difference is altogether insuffi- 
cient to introduce any noteworthy effects. 

Yenus is the only planet the extent of whose atmos- 



THE INFERIOR PLANETS. 91 

phere has been carefully estimated. 11 Venus had no 
atmosphere, she would present, when horned, a semicir- 
cular convexity; whereas the refractive effects of an 
atmosphere, by causing the sun to illumine rather more 
than a full hemisphere, would tend to lengthen her horns. 
It has been found that her convexity when she is horned 
exceeds a semicircle, and from the observed extent of 
this excess, it has been calculated that her atmosphere is 
so far more extensive than ours as to make its refractive 
effects on a body near the horizon about one-third great- 
er. So that, this being about the proportion in which 
the diameter of the sun as seen from Yenus exceeds that 
which he presents to us, the inhabitant of Venus, like the 
inhabitant of our earth, sees the sun fully raised above 
the horizon at the moment when, but for reflection, his 
orb would be just concealed beneath it. 

Of the constitution of the atmosphere of Venus we 
know little. The spectrum of her light shows the dark 
lines which belong to the solar spectrum, and the Padre 
Becchi has noticed certain faint lines, which seem to indi- 
cate the presence of aqueous vapor in the atmosphere of 
the planet. But he scarcely gives satisfactory evidence 
that the lines he has thus seen were not due to the absorp- 
tion exercised by aqueous vapor in our own atmosphere. 
The same observer finds, in the strengthening of the 
nitrogen lines near the F line of the spectrum, evidence 
that the atmosphere of Venus is constituted very simi- 
larly to the air we breathe. 



92 OTHER WORLDS THAN OURS. 

On the whole, the evidence we have points very strongly 
to Yenus as the abode of living creatures not unlike the 
inhabitants of earth. With the sole exception of the in- 
clination, which has been, without sufficient evidence, as- 
signed to the planet's equator, I can see nothing which 
can reasonably be held to point to an opposite conclusion. 
The strong light which the sun pours upon Yenus need 
least of all be objected to, since, if there is one adaptative 
power which Nature exhibits more clearly than another, 
it is that by which the various creatures we are acquainted 
with are enabled to live in comfort under all degrees of 
light, from the obscurity in which the mole pursues his 
subterranean researches, to the blazing light of the noon- 
day sun toward which (in fable, if not in fact) the eagle 
turns his unshrinking eyes. 

There is one peculiarity which yet remains to be no- 
ticed. Many are disposed to find, in the beauty of the 
celestial objects which deck the skies of different planets, 
a certain proof that reasoning beings must exist who can 
appreciate the display. Surely the argument has very 
little force, since we know that myriads on myriads of 
ages must have passed, during which the glories of our 
own heavens were displayed, night after night, with none 
to regard them. The moon has passed through all her 
phases, the star of morning and of eve has shed its soft 
radiance upon the terrestrial landscape, Jupiter and Sat- 
urn have pursued their stately courses among the fixed 
stars, and the glories of those constellations which shine 



THE INFERIOR PLANETS. 93 

with equal splendor upon all the planets of the solar 
scheme have been displayed in all their unchanging mag- 
nificence, while as yet our earth was the abode but of 
hideous reptiles, or of yet more monstrous creatures in 
forest and in plain. 

If this argument were really of force, doubtless there 
are no planets in the whole range of the solar system to 
which it might not be applied. Each has some special 
object of beauty in its heavens, which is not exhibited to 
the rest. Certainly Mercury and Yenus are no exceptions 
to this rule. The inhabitant of Mercury sees in Venus 
an orb which, when favorably situated, far outshines in 
splendor the brightest of the planetary orbs seen in our 
skies. So far, indeed, as light-giving power is concerned, 
Venus must be no contemptible moon to the Mercurials 
when she is nearly in opposition. Our earth, too, with 
its companion moon, must form a noble object in the sky 
of Mercury, though, without telescopic aid, the moon per- 
haps may not be separately visible. To the inhabitants 
of Venus, Mercury and the earth must be splendid ob- 
jects. The former would not only appear much larger 
than to ourselves, but being seen almost as favorably as 
we see Venus, would form a much more striking object in 
the morning or evening skies of that planet. The earth, 
as seen by the inhabitants of Venus, must shine much 
more splendidly than Jupiter does in our skies. Our 
moon must be distinctly visible, so that, without the aid 
of any telescope, the inhabitant of Venus has such evi- 



91 OTHER WORLDS THAN OURS. 

dence of the Copernican theory as would suffice, if prop- 
erly handled, to rout the ranks of the Ptolemaists, sup- 
posing there have ever been people in Yenus who im- 
agined the tiny globe they live upon to be the centre of 
the universe. 



MARS, THE MINIATURE OF OUR EARTH. 95 



CHAPTEE IV. 

MABS, THE MINIATUBE OF OUK EAETH. 

It is singular that, among all the orbs which circle 
around the sun, one only, and that almost the least of the 
primary planets, should exhibit clearly and unmistakably 
the signs which mark a planet as the abode of life. "We 
have examined Mercury and Venus, the only other orbs 
which belong like the earth and Mars to the scheme of 
the minor planets, and we have found little to guide us 
to any certain conclusion respecting their physical habi- 
tudes. When we pass beyond the wide gap which sepa- 
rates the minor planets from the giant members of the 
solar family, we shall find much to attract our admiration, 
much to force upon us the belief that these orbs have 
been created to be the abodes of even nobler races than 
those which subsist upon our earth ; but we shall find 
little to justify us in asserting that they resemble the 
earth in those habitudes which seem essential to the 
wants of terrestrial races. The planet Mars, on the other 
hand, exhibits in the clearest manner the traces of adap- 
tation to the wants of living beings such as we are ac- 
quainted with. Processes are at work out yonder in 
space which appear utterly useless, a real waste of Nat 



96 OTHER WORLDS TRAJST OURB. 

lire's energies, unless, like their correlatives on earth, 
they subserve the wants of organized beings. 

I would not indeed insist, as some have done, too 
strongly upon this argument. I know that on every side 
we see tokens of an exuberant activity in Nature, which, 
according to our ideas, may appear to savor of wasteful- 
ness. The cloud which has been raised by the solar 
energies from tropical seas, and which the winds have 
wafted over continents, may shed its waters on the sea 
or in the desert, where seemingly they are wholly wasted. 
Winds may spend their force apparently in vain. And 
in a thousand ways Nature's busy forces may be at work 
where we, in our short-sightedness, can see no useful pur- 
pose which they subserve. 

But there is a marked distinction between such ap- 
parent instances of wasteful action, and the systematic 
processes which are taking place over the globe of Mars. 

Upon our earth we can dimly trace out a necessity 
(depending upon the order which actually exists) for that 
which appears to resemble waste. "We see, for instance, 
that if a country or a continent is to be provided with a 
due supply of rain, without supernatural intervention at 
every step of the process, that result can only be secured 
by what may be described as a random distribution, in- 
volving always what to us resembles waste. If, out of a 
thousand showers, ten only fall so as to be useful to the 
land, the useful rainfalls serve to explain (so to speak) the 
geemingly wasted ones. 



MARS, THE MINIATURE OF OUR EARTH. 97 

In the case of Mars we have no such explanation of 
the processes we observe, if we dismiss our belief that he 
is the abode of liying creatures. For if Mars be, indeed, 
untenanted by any forms of life, then these processes, 
going on year after year and century after century, repre- 
sent an exertion of energy which appears absolutely with- 
out conceivable utility. If one cloud out of a hundred 
of those which shed their waters upon Mars supplies in 
any degree the wants of living creatures, then the purport 
of those clouds is not unintelligible ; but if not a single 
race of beings peoples that distant world, then indeed we 
seem compelled to say that in Mars at least Nature's 
forces seem wholly wasted. 

L»et us consider what astronomy has taught us respect- 
ing the ruddy planet. 

The globe of Mars is about five thousand miles in di- 
ameter, so that his linear dimensions bear to those of the 
earth the proportion of about five to eight. His surface, 
therefore, is less than that of the earth in the proportion 
of about twenty-five to sixty-four, or more exactly (and 
more conveniently), the surface of the earth is two and a 
half times as extensive as that of Mars. 

The substance of Mars has an average density rather 

less than three-fourths of our earth's, or very nearly four 

times that of water. Thus gravity at his surface is much 

less than terrestrial gravity. It is even less, in fact, than 

gravity at the surface of Mercury, insomuch that one of 

our pound weights placed at the surface of Mars would 
7 



98 OTHER WORLDS THAN OURS. 

weigh but 6 oz. 3 dwts., instead of nearly seven ounces, 
as on Mercury. I have already dwelt on the effects of 
such a relation as this, and shall have occasion, when de- 
scribing the condition of Jupiter, to discuss the converse 
relation. But I may remark, in passing, how singular it 
is that we should be compelled to people the smallest 
planets with the largest inhabitants, if we wish to bring 
the inhabitants of different orbs to about the same scale 
of activity. A Daniel Lambert on Mars would be able 
to leap easily to a height of five or six feet, and he could 
run faster than the best of our terrestrial athletes. A 
man of his weight, but proportioned more suitably for 
athletic exercises, could leap over a twelve-foot wall. On 
the other hand, a light and active stripling removed to 
Jupiter would be scarcely able to move from place to 
place. On the sun his own weight would simply crush 
him to death. 

Mars travels in an orbit of considerable eccentricity ; 
in fact, the centre of his orbit is no less than thirteen 
million miles from the sun. Accordingly, the light and 
heat he receives from that luminary vary to an important 
extent. In fact, he gets about half as much heat and light 
again when in perihelion as when in aphelion. This cir- 
cumstance affects to an important extent the climatic re- 
lations of his two hemispheres, as we shall presently see. 

When Mars is at his mean distance from the sun, the 
light and heat he receives are less than ours in the pro- 
portion of about 4 to 9. The length of his year also 



MARS, THE MINIATURE OF OJfR EARTH. 99 

constitutes a noteworthy circumstance in which his hab- 
itudes differ from those of our earth. His year con- 
tains very nearly 687 of our days, so that each of the 
Martian quarters lasts about 5§ of our months. But, 
owing to the eccentricity of his orbit, the winter and 
summer of the northern and southern hemispheres are 
not equal. The Martian day is nearly forty minutes 
longer than ours.* 

His equator is inclined at an angle of about 27J° to 
the plane of his orbit, and as the corresponding inclina- 
tion in the case of the earth is about 23^°, it will be 
seen that his seasonal changes do not differ much in 
character, so far at least as they depend on inclination, 
from our own. 

The axis of Mars is so situated that the summer of his 
northern hemisphere occurs when he is at his greatest 
distance from the sun. The same relation holds in the 
case of the earth, the sun being one million five hun- 
dred thousand miles nearer to us in winter than in sum- 
mer, whereas, to those who live in the southern hemi- 
sphere, he approaches nearer in summer than in winter. 



* More exactly, the length of the Martian day is 24h. 37m. 22.7s. 
This estimate I have obtained by comparing pictures taken by Hooke 
in 1666, and by Dawes and Browning in 1866-69 — taking precautions 
to secure that no complete rotation should anywhere be lost sight of. 
Kaiser obtained a period differing only one-tenth of a second from 
mine ; but even this small discrepancy is removed when certain cleri- 
cal errors in Kaiser's work (as his counting 1700 and 1800 as leap-years, 
»nd wrongly correcting for change of style) are removed. 

ILofC. 



100 OTHER WORLDS THAN OURS. 

But the effects resulting from the relation in the case of 
Mars must be very much more striking than those we 
recognize. For whereas the sun gives only one-fifteenth 
more heat to the whole earth in January than he does in 
July, the sun of Mars gives half as much light again in 
perihelion as in aphelion. The summer of the northern 
hemisphere of Mars must be rendered much cooler aud 
the winter much warmer by this arrangement. On the 
other hand, the contrast between the summer and winter 
of the southern hemisphere is rendered more striking 
than it otherwise would be. 

It is, however, the telescopic aspect of Mars rather than 
relations such as we have been dealing with that affords 
the most interesting evidence respecting the fitness of 
the planet to be the abode of living creatures. Although 
the least but one among the primary planets — a mere 
speck compared with Jupiter and Saturn — Mars has been 
examined more minutely and under more favorable cir- 
cumstances than any object in the heavens except the 
moon. He does not approach us so closely as Venus, nor 
does his disk appear so large as Jupiter's, yet he is seen 
more favorably than the former planet, and on a larger 
scale, in reality, than the latter. In fact, whereas Yenus 
is one of the most unsatisfactory of all telescopic objects^ 
Mars is one of the most pleasing ; and whereas Jupiter is 
always more than 380,000,000 of miles from us, Mars 
sometimes approaches us within less than 40,000,000 of 
miles. 



MARS, THE MINIATURE OF OUR EARTH. 101 

Tet even this distance is enormous, and it affords high 
evidence of the skill with which modern telescopes are 
constructed and used that astronomers should have been 
able to span that mighty gulf, and to bring from beyond 
it reliable information respecting the structure of so dis- 
tant a world. 

Such information has been brought, however, and is 
full of interest. 

Viewed with the naked eye, the most remarkable feat- 
ure Mars presents is his ruddy color. In the telescope 
this color is not lost, but instead of characterizing the 
whole surface of the planet, it is confined to particular 
regions — the intermediate parts being for the most part 
darker, and of a somewhat greenish hue. But a note- 
worthy feature adds largely to the beauty of the picture 
presented by the globe of Mars. Two bright spots of 
white light are seen on opposite sides of his disk, pre- 
senting precisely such an appearance as we might ima- 
gine the snowy poles of our earth to exhibit to an astron- 
omer on the planet Venus. 

Toward the edge of the disk the ruddy and the greenish 
tracts are lost in a misty whiteness, which grows gradu- 
ally brighter up to the very border of the planet. This 
peculiarity, as will be seen, is one of the most instructive 
features of the planet's aspect. 

In August, 1877, two minute moons were discovered 
which travel around Mars in about 30J hours and about 
7| hours respectively. 



102 OTHER WORLDS THAN OURS. 

It was discerned, more than two hundred years ago, 
that the reddish spots on Mars, and the darker regions 
which lie between them, are not accidental or variable 
phenomena, but represent permanent peculiarities of the 
Martian surface. Cassini, with one of those outrageously 
long telescopes which were used before the invention 
of achromatic refractors, was the first to discover this. 
But the ingenious Hooke seems to have obtained better 
views of Mars in 1666. At least, his pictures of the 
planet are the only ones taken in the seventeenth cen- 
tury in which I can recognize the now well-known aspect 
of the Martian continents and oceans. 

Later, Maraldi and the Herschels, Arago, Secchi, Ku- 
nowski, Beer, and Madler, and a host of other eminent 
astronomers, have not thought the study of this planet's 
aspect beneath their notice. "Within the last few years, 
also, this work has been prosecuted by Dawes, Green, B. 
Trouvelot, and others. Dawes, whose acuteness of vision 
earned for him the title of the " eagk-eyed," took so 
many and such admirable views of the planet as to render 
it possible to form a globe of Mars. Sir William Herschel 
had charted the planet, and Messrs. Beer and Madler had 
made improved Martian maps; while Phillips had con- 
structed two globes of Mars in which many features were 
presented. But Mr. Dawes's pictures of the planet were 
sufficient, when carefully compared, for the formation of 
a globe in which no large area of the planet should be 
left bare of details. He intrusted to me no less than 



MAMS, THE MINIATURE OF OUR EARTH. 103 

twenty-seven drawings of Mars, the choicest specimens of 
a very large series, that I might chart the planet from 
them. From the study of his drawings the chart illus- 
trated in Fig. 1 has been formed. Of the four illustrative 
views, the upper were drawn by Mr. Trouvelot at Har- 
vard, the lower by Mr. Nath. Green. The chart of Mars, 
in which the darker parts of the planet are assumed to be 
seas and the lighter tracts continents, exhibits the results 
obtained from the study of the complete series. This 
chart is on Mercator's projection, and is inverted — the 
south polar regions, that is, are at the top — because the 
telescopes commonly used by observers exhibit inverted 
views of the celestial objects. At the top of the map wn 
see the icy region which lies at the southern pole of Mars 
Around that region is a sea unnamed in the maps. Then 
along the southern temperate zone there lie several tracts 
of Martian land, named after observers of the planet. 
These regions appear to form a continuous land-belt 
round the temperate zone ; though there is some uncer- 
tainty on this point, owing to the fact that the coast-line 
is not often very distinctly visible. "We now approach, 
however, a part of the map where all the features are 
thoroughly recognized and permanent. Next to the circle 
of land just described there is a nearly complete circle of 
water, one strip only of land connecting the equatorial 
continents of Mars with the south temperatate zone of 
minor continents. Beginning at the eastern or left-hand 
extremity of the map, we have a long sea called Maraldi 



104 OTHER WORLDS THAN OURS. 

Sea, parallel to which runs Hooke Sea, trending in a 
northwest srly direction, and so running into Dawes 
Ocean ; still further west are two vast islands, called 
Jacob Island and Phillips Island, between which runs 
Arago Strait. Beyond these islands lies De la Rue 
Ocean, communicating by narrow straits with two strik- 
ingly similar seas. Here the zone of water ends, and we 
have only to note further respecting it that in De la Rue 
Ocean there is a large island, which presents so strikingly 
brilliant an aspect that it has been supposed to be cov- 
ered (ordinarily) with snow. It has been called Dawes's 
Ice Island. 

I now come to the most remarkable feature of the Mar- 
tian geography — or perhaps I ought rather to say, areog- 
raphy. This is the great equatorial zone of continents. 
There are four of these. On the left of the map (Fig. 2) 
is Herschel I. Continent. Next is Dawes Continent, the 
largest of the four, and separated from the former by a 
long sea called Kaiser Sea. This sea is one of the most 
striking marks on the planet, and has been recognized 
from the earliest days of telescopic observation. It is 
connected toward the east with a flask-shaped sea, some- 
what resembling the two which lie at the western extrem- 
ity of the zone of water just described. At its northern- 
most end it turns sharply westward, and forms the 
southern boundary of Dawes Continent. Further west 
lies Madler Continent, separated from Dawes Continent 
by a long strait, which runs almost directly north and 



MARS, THE MINIATURE OF OUR EARTH. 105 

south. Lastly, there is Secchi Continent, separated 
from Madler Continent by Bessel Inlet and from Her- 
schel Continent by Huggins Inlet. A large lake on the 
last-named continent is worthy of notice on account of 
its singular shape. It consists of two bell-shaped seas 
connected by a narrow and sharply curved strait. 

The northern half of Mars has not been so thoroughly 
examined as the southern, for a reason which will pres- 
ently be mentioned. It is known, however, that, in all 
essential respects, it resembles the southern hemisphere. 
Next to the equatorial zone of continents there comes a 
zone of water, expanding at one point into Beer Sea, and 
at another into Tycho Sea. Then comes a zone of land, 
called Laplace Land, in which lies an enormous lake 
called Delambre Sea. Next is a narrow zone of water, 
called the Schroter Sea : and so we reach the north polar 
ice-cap. 

I have been speaking of the spots on Mars as though 
they undoubtedly represented land and water. But 
many may be disposed to question the evidence we have 
on this point — to ask why the ruddy spots should be 
held to be continents or islands, and the greenish-colored 
markings to be oceans, seas, and lakes. "We know that 
for a long time after the invention of the telescope, as- 
tronomers called the darker portions of the moon, seas. 
They spoke of the Sea of Serenity, the Sea of Crises, the 
Sea of Humors, and so on ; and we know now for certain 
that these dusky regions are not seas. It may be asked, 



106 OTHER WORLDS THAN OURS. 

therefore, how we can feel certain that the dark spots on 
Mars are oceans. 

At first sight this question seems a difficult one to an- 
swer. The most powerful telescopes have been directed 
toward the moon, without affording any satisfactory in- 
formation respecting the condition of its surface. Mars, 
therefore, which lies — even under the most favorable cir- 
cumstances — more than one hundred and sixty times 
further from us than the moon, might be thought to be 
altogether beyond the reach of our telescopists — so far, 
at least, as any knowledge of the Martian surface is con- 
cerned. But one important distinction between Mars 
and the moon must be carefully attended to. The 
surface of the moon is always the same — no natural 
processes seem ever to take place over that scene of deso- 
lation, though the moon is exposed to contrasts of tem- 
perature, compared with which the distinction between 
the intensest heat of our summers and the bitterest cold 
of our winters seems altogether evanescent. But on 
Mars the case is certainly different. Whatever opinion 
we may form respecting Martian habitudes, whether we 
assume or not that Mars is the abode of any forms of 
animal life, there can be no question whatever that physi- 
cal processes of change are taking place on a grand 
scale in that distant world. Many evidences of this can 
be at once adduced. We have spoken of the Martian 
features as constant. They differ, for instance, from the 
markings on Jupiter, which are as changeful as the as- 



MAES, THE MINIATURE OF OUR EARTH. 107 

pect of our April skies. But though the same marking 
may have been seen by Hooke in 1666, by Maraldi in 
1720, by Herschel in 1780, by Beer and Madler in 
1830-37, and by Dawes in 1852-65, yet it by no means 
follows that it is always visible when the part of 
Mars to which it belongs is turned toward us. A veil is 
sometimes drawn over it for hours or even days together. 
And this veil has nothing to do with the distinctness or 
indistinctness with which our own atmosphere permits us 
to see the planet. A spot will be blurred and indistinct 
when a neighboring marking is exhibited with unusual 
clearness. 

Let us consider an instance of this peculiarity. On 
October 3, 1862, late in the evening, a part of Dawes 
Ocean, where it borders on Herschel Continent, was hid- 
den from view. In place of the ordinarily dark aspect 
of this region, a faint, misty light, with ill-defined bor- 
ders, was observable. As the evening progressed the 
outlines gradually became clearer, but at about half-past 
eleven the white light still continued to veil the outline 
of a part of Dawes Ocean. But Mr. Dawes, observing 
Mars at a quarter past twelve, found that the process of 
clearing up noticed in the earlier part of the night had 
entirely lifted off the veil which concealed the coast-line. 
The remains of the misty light seen earlier are still to be 
detected in Mr. Dawes's drawing, but they have passed 
further south, and no longer hide the shores of Dawes 
Ocean, 



108 OTHER WORLDS THAN OURS. 

The Padre Secchi of the Collegio Eomano states that 
he has often noticed similar appearances while observing 
Mars with the fine refractor in the observatory of that 
institution. 

But yet another peculiarity of the same sort remains 
to be mentioned. Mars, as I have said, has his winter 
and summer seasons. Since we know the position of 
the Martian equator upon his surface, we can tell what 
season is in progress in either hemisphere at any given 
time. Now, it has been noticed that when it is winter in 
one hemisphere, and therefore summer in the other, the 
former hemisphere is nearly always hidden from view 
by just such a veil as I have spoken of above. 

I may remark, in passing, that this peculiarity has led 
many observers to form very erroneous impressions re- 
specting the distribution of land and water over the sur- 
face of Mars. Seeing one hemisphere covered for weeks 
together with whitish light, they have concluded that 
there are no oceans there ; and if they have no other op- 
portunity of observing the planet, the mistaken impres- 
sion remains, and is published to the world with all the 
authority of the observer's name. 

Now, what is this veil which sometimes for a few hours 
or days, at others for months together, is drawn over the 
features of the Martian globe ? Have we any terrestrial 
analogies by means of which we may interpret this phe- 
nomenon? 

To answer these questions, let us conceive the case of 



MAES, THE MINIATURE OF OUR EARTH. 109 

an observer on Venus watching our earth. Would such 
an observer always see the features of this globe with 
equal distinctness ? When heavy masses of cloud are 
drawn over a wide expanse of country — spreading often, 
as meteorologists record, for hundreds, and even thou- 
sands of miles — can we suppose that the astronomer on 
Yenus could pierce through the veil ? Since we cannot 
see the bright body of the sun through a dense cloud- 
veil, we may be certain that the observer on Yenus can- 
not see the oceans and continents of our earth when thus 
cloud-shadowed. So far as the cloud-veil extends, the 
lands and seas of this globe would be to him, at such a 
time, as though they were not. 

Here, then, we have an argument from analogy for 
supposing that the veil, which from time to time con- 
ceals the Martian features, may resemble terrestrial 
cloud-banks. Let us next inquire whether there is any- 
thing in the behavior of the Martian veil to justify this 
view. 

It is clear that if we held the concealing medium to be 
of a cloudy nature, the disappearance of the features of 
the hemisphere which is passing through the Martian 
winter would indicate that in winter the Martian skies 
are more clouded than in summer. We know that this 
is the case on our own earth, that fogs and mists, clouds, 
rain, and snow, are phenomena far more frequently ob- 
served in winter than in summer. We know also why 
it is so. The cold winter air is unable to . retain the 



110 OTHER WORLDS THAN OURS. 

aqueous vapor continually passing into it, and is thus 
forced to precipitate this vapor in one or other of the 
forms just named. Nor can we see any reason why the 
Martian atmosphere, supposing it to resemble our own, 
should not act in precisely the same manner. Thus we 
recognize, in the remarkable seasonal peculiarity above 
described, what seems to be the exact counterpart of 
processes recognized upon the earth. 

Perhaps the reader may be disposed to inquire 
whether the clearing up of a portion of the Martian disk 
observed by Dawes admits of interpretation in a similar 
way. To this it may be replied that, from the observed 
position of the region in question, the Martian time of 
day there must have been somewhere about noon, and 
about one o'clock in the afternoon (according to our ter- 
restrial mode of reckoning) when Mr. Dawes observed 
the planet. It is no uncommon thing to see our terres- 
trial skies clear up soon after midday; and if the veil 
which conceals the Martian features is really cloudy, 
this is precisely what happened out yonder, forty mill- 
ions of miles away from us, on the day in question. 

I think the reader will at least concede that the expla- 
nation here given of these peculiarities is more natural 
than one which was put forward some time since by an 
eminent French astronomer. He urged that Martian 
vegetation, instead of being green like ours, is red ; 
hence in the Martian summer, the surface, as seen by 
us, assumes a ruddy aspect, while the wintry hemisphere 



MARS, THE MINIATURE OF OUR EARTH. Ill 

loses its ruddy tint. According to this interpretation, 
such changes as were noticed by Secchi would indicate 
the sudden blooming forth of Martian vegetation over 
hundreds of square miles of the Martian surface ! 

To the evidence already dealt with may be added that 
which is afforded by the whiteness of the disk of Mars 
near the edge. Knowing that the parts of Mars which 
thus appear concealed in mist are those where it is morn- 
ing or evening to the Martians, we see a close analogy 
\iere to terrestrial relations, since our own skies are com- 
monly more moisture-laden in the morning and evening 
than near midday.* 

I may here pause, in passing, to notice under what 
difficulties the observation of Mars is conducted by the 
terrestrial observer. To begin with, the sky must be 
exceptionally clear ; and none but the practised observer 
knows how seldom there occurs what is called " a good 
observing night." Then it must be ajine day for the 
Martians, for clouds over Mars, or even an imperfectly 
clear atmosphere, must produce quite as bad an effect in 
spoiling the definition of Martian features as similar 



* In the Popular Science Review for January, 1869, I have in- 
dicated a subsidiary explanation of this peculiarity, founded on the 
probable shape of the Martian clouds. For the same reason that, near 
the horizon, our own cumulus clouds seem more closely packed than 
overhead, the Martians would see a clearer sky overhead than near the 
horizon. It follows at once that we should see best those parts of the 
surface of Mars which we look down upon in an early vertical direc- 
tion, that is, the central parts of his disk. 



112 OTHER W0RLD8 THAN OURS. 

phenomena on earth. Again, Mars only comes into a 
favorable position once in every two and a quarter years, 
continuing to be well placed for only a Jew months. 
Thus it happens that, although Mars has been telescopi- 
cally observed for more .than two hundred years, the 
actual time during which he has been favorably placed for 
observation has been very much less; and taking into 
account all the requirements for good definition, it may 
be said that Mars has not been under really effective ob- 
servation for more than a very few days. 

Of course if we admit that the vaporous envelope which 
occasionally hides parts of Mars is aqueous, we must 
believe in the existence of oceans upon Mars. And from 
our knowledge of the appearance of our own seas, we 
should immediately recognize the greenish parts of Mars 
as the Martian oceans, and look upon the ruddy parts as 
continents. "We have seen that the behavior of the vari- 
ous envelopes corresponds to that of our own clouds and 
fogs. But it might be thought possible that the vapors 
arise from fluids other than water ; that, in fact, a state of 
things exists upon Mars wholly different from that which 
prevails upon our own earth. 

A few years ago it would have been very difficult to 
disprove such an argument as this, however fanciful it 
may seem. But the wonderful powers of the spectroscope 
have been applied to this question, and there is no mis- 
taking the results which have been obtained. We must 
premise that this is hardly a favorable case for the appli- 



MAR8. THE MINIATURE OF OUR EARTH. 113 

cation of spectroscopic analysis, which (as available to 
the astronomer) deals most effectively with self-luminous 
objects. Still, there was a possibility that the light 
which comes from Mars might have been so acted upon 
by vapors in the Martian atmosphere that its spectrum 
would be affected in an appreciable manner. 

Mr. Huggins examined Mars in 1864 without satisfac- 
tory results, but at the opposition of Mars in 1867 he 
was more successful. In the following description of his 
most striking observation I epitomize his account. On 
the 14th of February he examined Mars with a spectro- 
scope attached to his powerful 8-inch refractor. The 
rainbow-colored streak was crossed, near the orange part, 
by groups of dark lines agreeing in position " with lines 
which make their appearance in the solar spectrum when 
the sun is low down so that its light has to traverse the 
denser strata of out- atmosphere." To determine whether 
these lines belonged to the light from Mars or were 
caused by our own atmosphere, Mr. Huggins turned his 
spectroscope toward the moon, which happened to be 
nearer the horizon than Mars, so that the atmospheric 
lines would be stronger in the moon's spectrum than in 
that of the planet. But the group of lines referred to was 
not visible in the lunar spectrum. Hence it was clear that 
they belonged to the Martian atmosphere, and not to ours. 

I have said that these lines appear in the solar spec- 
trum when the sun is shining through the denser strata 

of our atmosphere ; so that the Martian atmosphere must 
8 



114 OTHER WORLDS THAN OURS. 

contain at least those constituent vapors whose existence 
in our atmosphere causes the appearance of these lines in 
the solar spectrum. Hence there must be some similarity 
between the Martian atmosphere and our own. But we 
know from the researches of the Padre Secchi that it is 
the aqueous vapor in our air which causes the appearance 
of the lines in question. Hence there must be aqueous 
vapor in the Martian atmosphere. 

The discovery at once justifies the title of the present 
chapter. Let us consider what a number of interesting 
results follow from it. 

The water in the Martian air must be raised from seas 
and rivers upon the planet. These, therefore, consist of 
water, and not of other fluids. The two white spots, then, 
on the Martian disk are no longer doubtful appearances. 
Before the discovery that water exists on Mars it was 
perhaps somewhat bold to pronounce that these spots 
certainly indicate the presence of ice-fields around the 
Martian poles, resembling those which exist around the 
poles of the earth. Sir William Herschel, indeed, with 
that confidence which he always showed when he had a 
trustworthy analogy to guide him, came to this conclu- 
sion on the strength of the correspondence between the 
changes of the two spots and the progress of the Mar- 
tian seasons. But many astronomers felt that there was 
still room to doubt whether he could really speak of the 
spots as 

The snowy poles of moonless Mars. 



MARS, THE MINIATURE OF OUR EARTH. 115 

Now, however, we know that they can be no other than 
snow-caps. Nay, if Mars were so far off that we could 
not distinguish these spots, we could yet, on the strength 
of what the spectroscope has taught us, pronounce confi- 
dently that his polar regions must be ice-bound. 

Let us proceed a step or two further. We have seen 
that there are oceans on Mars ; we know that clouds and 
vapors arise from those oceans, and are wafted over his 
continents ; and finally, we have learned that snow falls 
on the Martian polar regions. These facts are very inter- 
esting in themselves, but they indicate the occurrence of 
processes yet more interesting. The formation and the 
dissipation of clouds are among the most important of all 
the processes by which Nature arranges and modifies the 
temperature of our earth. The heat of the sun's rays is 
used up, so to speak, in raising aqueous vapor from the 
surface of the ocean. Thus the air is rendered cooler 
than it otherwise would be, and this takes place just 
where coolness is most needed. But the aqueous vapor, 
once raised, is swept by the winds to other regions. So 
long as the air remains warm the aqueous vapor remains 
unchanged ; but so soon as it has been carried to colder 
regions it is condensed into the form of a cloud or mist, 
and while changing to this form it parts with the heat 
which had turned it into vapor. Thus where heat is in 
excess, it is used up in forming aqueous vapor; and 
where heat is wanted, there the aqueous vapor distrib- 
utes it. 



116 OTHER WORLDS THAN OURS. 

"We see 9 then, that on Mars there exists the same ad- 
mirabio contrivance for tempering climates which we find 
on our own earth. 

But let us consider yet another office fulfilled by aque- 
ous vapor. It not only serves to convey the heat from 
the warmer parts of the earth to those regions where heat 
is most needed ; it forms clouds which serve to shelter the 
earth from the sun's heat by day, and to prevent the es- 
cape of the earth's heat by night, which also, in refresh- 
ing rains, " drop fatness on the earth." Now the clouds 
on Mars are certainly dissipated in some way, because, as 
I have said, astronomers have repeatedly seen them dis- 
appear. And doubtless, like our own clouds, they are 
often dissipated by the sun's heat. But we may take it 
for granted that, like our terrestrial clouds, they are also 
often dissipated by falling in rain. Thus the Martian 
lands are nourished by refreshing rainfalls ; and who can 
doubt that they are thus nourished for the same purpose 
as our own fields and forests — namely, that vegetation of 
all sorts may grow abundantly ? 

But yet again, the transit of clouds from place to place 
implies the existence of aerial currents. Clouds cannot 
indeed even form and be dissipated without occasioning 
wind-currents ; and it need hardly be said that the Mar- 
tian clouds could not be carried to his polar regions, 
there to fall in snow, unless the atmospheric currents on 
Mars were extensive and persistent. We see, then, that 
Mars has winds as our earth has. Doubtless his trade- 



MARS, THE MINIATURE OF OUR EARTH. 11? 

winds are less marked than ours, because his surface 
rotates less rapidly than the earth's, his globe being much 
smaller, while his rotation-period is slightly greater. But 
he has less need for trade-winds, his oceans being so 
much less extensive than ours. No Columbus on Mars 
has ever needed the persistent breath of easterly winds 
to encourage him on his voyage to an undiscovered con- 
tinent. Rather, the intricate navigation of the narrow 
Martian seas would be favored by variable breezes. But 
the great purposes which the circulation of our own 
atmosphere subserves are subserved efficiently out yonder 
on Mars. The air is cleansed and purified, its thermal 
and electrical conditions are regulated, clouds are wafted 
from place to place; and, in fine, the atmosphere is 
rendered fit for all those purposes for which, like our 
own, it has doubtless been created. 

We may trace yet further, however, the results which 
follow from the existence of aqueous vapor in the atmos- 
phere of Mars. We see the polar snows aggregating in the 
Martian winter and diminishing in the Martian summer. 
And we know that, on our own earth, the increase and the 
diminution of the polar snows are processes intimately 
associated with the formation and maintenance of the 
oceanic circulation. Doubtless much yet remains to be 
done before that system of circulation will be fully under- 
stood. The rival views which have been maintained by 
Sir John Herschel and Captain Maury have served to 
throw a certain air of doubt over the theory of ocean cur' 



118 OTHER WORLDS THAN OURS. 

rents. * But whether we ascribe the equatorial currents 
of our oceans to the trade-winds, with Herschel, or to 
differences of specific gravity, with Maury, we see that, in 
the first place, both causes operate in the case of Mars ; 
and, secondly, that the submarine return-currents from 
our polar regions must, at any rate, be due to the presence 
of ice in the polar seas. So that undoubtedly the Mar- 
tian oceans, so far as their peculiar conformation will 
permit, are traversed by currents in various directions and 
at various depths. 

Then, lastly, there must be rivers on Mars. The clouds 
which often hide from our view the larger part of a Mar- 
tian continent indicate a rainfall at least as considerable 
(in proportion) as that which we have on the earth. The 
water thus precipitated on the Martian continents can find 
its way no otherwise to the ocean than along river courses. 

As to the nature of these rivers, again, we may form 
conjectures founded on trustworthy analogies. The mere 

*If Herschel has completely overthrown Maury's theory, that cur- 
rents are altogether due to differences of specific gravity, saltness, and 
so on, Maury has at least been as successful in overthrowing Herschel's 
theory, that the currents are due to the trade-winds. A theory more 
probable than either is, I think, that according to which the whole 
system of circulation is set in motion by the continual evaporation going 
on in equatorial seas. Thus, by a process resembling suction, an in- 
draught of cold water is caused, and this water coming from higher 
latitudes, where the earth's eastwardly motion is less, to lower latitudes, 
where the eastwardly motion is greater, produces the relatively cold and 
westwardly equatorial currents which exist in the Atlantic, Indian, and 
Pacific oceans. Recent researches into the temperature of the deep sea 
have tended strongly to confirm these views, which I dealt with at some 
length in the second volume of my Light Science for Leisure Hours. 



MAES, THE MINIATURE OF OUR EARTH. 119 

existence of continents and oceans on Mars proves the 
action of forces of upheaval and of depression. There 
must be volcanic eruptions and earthquakes modelling 
and remodelling the crust of Mars. Thus there must be 
mountains and hills, valleys and ravines, water-sheds and 
water-courses. All the various kinds of scenery which 
make our earth so beautiful have their representatives in 
the ruddy planet. The river courses to the ocean, by cata- 
ract and lake, here urging its way impetuously over rocks 
and bowlders, there gliding with stately flow along its more 
level reaches. The rivulet speeds to the river, the brook to 
the rivulet, and from the mountain recesses burst forth the 
refreshing springs which are to feed the Martian brooklets. 
Who can doubt what the lesson is that all these things 
are meant to teach us? So far, let it be remembered, we 
have been guided onward by no speculative fancies, but 
simply by sober reasoning. But shall we recognize in 
Mars all that makes our own world so well fitted to our 
wants — land and water, mountain and valley, cloud and 
sunshine, rain and ice and snow, rivers and lakes, ocean- 
currents and wind-currents — without believing further in 
the existence, either now, or in the past, or in the future, 
of many forms of life ? Surely, if it is rashly speculative 
to form such an opinion respecting this charming planet, 
it is to speculate still more rashly to assert that Mars is 
not, has never been, and never will be, tenanted by living 
creatures, or by any beings belonging to other than the 
lowest orders of animated existence. 



120 OTHER WORLDS THAN OURS. 



CHAPTEE V. 

JUPITER, THE GIANT OF THE SOLAR SYSTEM. 

Passing over the zone of asteroids, we come now to the 
noblest of all the planets — the giant Jupiter. If bulk is 
to be the measure of a planet's fitness to be the abode of 
living creatures, then must Jupiter be inhabited by the 
most favored races existing throughout the whole range 
of the solar system. Exceeding our earth some one 
thousand two hundred and thirty times in volume, and 
more than three hundred times in mass, this magnificent 
orb was rightly selected by Brewster as the crowning 
proof of the relative insignificance of the earth in the 
scale of creation. 

Or if we estimate Jupiter rather by the forces inherent 
in his system, if we contemplate the enormous rapidity 
with which his vast bulk whirls round upon its axis, or 
trace the stately motion with which he sweeps onward on 
his orbit, or measure the influences by which he sways 
his noble family of satellites, we are equally impressed 
with the feeling that here we have the prince of all the 
planets, the orb which, of all others in the solar scheme, 
suggests to us conceptions of the noblest forms of life. 

The very symmetry and perfection of the system which 



JUPITER, GIANT OF THE SOLAR SYSTEM. 121 

circles round Jupiter have led many to believe that he 
must be inhabited by races superior in intelligence to any 
which people our earth. The motions of these bodies 
afford, indeed, to our astronomers a noble subject of 
study. Our most eminent mathematicians have given 
many hours of study to the phenomena which the four 
moons present to the terrestrial observer. But we can 
trace only the general movements of the satellites of 
Jupiter. Their minor disturbances, the effects of the 
varying influences which the sun and Jupiter exert upon 
them, and which the moons exert upon each other, must 
tax the powers of far abler mathematicians even than 
tie who " surpassed the whole human race in mental 
grasp." 

But, after all, we must judge of Jupiter rather accord- 
ing to the evidence we have, and the analogies which are 
most directly applicable to the case, than according to 
fancies such as these. We know that the sun, which sur- 
passes Jupiter in weight and volume even more than Jup- 
iter surpasses the earth, is yet not the abode of life, so 
that mere size and mass must not be held to argue habit- 
ability. "We know that many meteors and comets sweep 
through space more swiftly than the vast bulk of Jupiter, 
so that the energies indicated by mere velocity of motion, 
whether orbital or rotational, must be equally disregarded. 
Nor must we forget that, ages before men studied the 
motions of our own moon, she presented the same noble 
subject of study that she forms in our day for an Adams, 



122 OTHER WORLDS THAN OURS. 

a Leverrier, or a Delaunay. Even now a thousand grand 
problems are presented to our men of science which es- 
cape their notice, and we might as reasonably argue that 
there must be creatures existing unperceived among us, 
who deal with these problems, as that, out yonder in 
space, there must be beings who study the complicated 
motions of the Jovian satellites. 

Jupiter presents the following principal physical habi- 
tudes : 

He has a diameter of about eighty-five thousand miles, 
or nearly eleven times as large as the earth's, a surface 
one hundred and fifteen times larger, and, as I have said, 
a volume more than one thousand two hundred times 
larger. Gravity at his surface is about two and a half 
times as great as on our earth's, so that such creatures as 
exist around us would find their weight much more than 
doubled if they were removed to Jupiter. He lies more 
than frve times further from the sun than our earth, and 
the light and heat which he receives from that orb are 
reduced to about one-twenty-fifth of our supply. He 
rotates on his axis in rather less than ten hours (9 hours, 
55 minutes, 26 seconds), so that the length of his day is 
considerably less than half of ours. His axis is nearly 
perpendicular to his orbit, so that there are no apprecia- 
ble seasonal changes as he sweeps round the sun in his 
long year of 4,332£ days. 

It will be convenient to consider, first, the probable 
influence of the great attractive power of Jupiter upon the 



JUPITER, GIANT OF THE SOLAR SYSTEM. 123 

dimensions of the various orders of Irving creatures exist* 
ing upon his surface. 

The grandeur of his orb naturally suggests, at first 
sight, the idea of beings far exceeding, both in might and 
bulk, those which live upon the earth. Old Wolfius was 
led to a similar conclusion in another way. I quote his 
quaint fancies as quaintly presented by Admiral Smyth. 
"Wolfius," says the genial sailor, "not only asserts that 
there are inhabitants in Jupiter, but also shows that they 
must necessarily be much larger than those of the earth ; 
in fact, that they are of the giant kind, and nearly four- 
teen feet high by e?/e-measurement. And thus he proves 
it. It is shown in optics that the pupil of the eye dilates 
and contracts according to the degree of light it encoun- 
ters. Wherefore, since in Jupiter the sun's meridian 
height is much weaker than on the earth, the pupil will 
need to be much more dilatable in the Jovian creature 
than in the terrestrial one. But the pupil is observed to 
have a constant proportion to the ball of the eye, and the 
ball of the eye to the rest of the body ; so that, in ani- 
mals, the larger the pupil the larger the eye, and conse- 
quently the larger the body. Assuming that these con- 
ditions are unquestionable, he shows that Jupiter's dis- 
tance from the sun, compared with the earth's, is as 26 
to 5 ; the intensity of the sun's light in Jupiter is to 
its intensity on the earth in a duplicate ratio of 5 to 
26." The eyes of the Jovians and their dimensions gen- 
erally must be correspondingly enlarged, and " it there- 



124 OTHER WORLDS THAN OURS. 

fore follows that even Goliath of Gath would have cut 
but a sorry figure among the natives of Jupiter. That is, 
supposing the Philistine's altitude to be somewhere be- 
tween eight feet and eleven, according as we lean to 
Bishop Cumberland's calculation, or the Vatican copy of 
the Septuagint. Now, Wolfius proves the size of the 
inhabitants of Jupiter to be the same as that of Og, king 
of Bashan, whose iron camp-bed was nine cubits in length 
and four in breadth — or rather he shows, in the way 
stated, the ordinary altitude of the Jovicol«3 to be 13-j^y^ 
Paris feet, and the height of Og to have been 13} 1 1-§ feet. 
See his Works, vol. iii., p. 438." 

This exact determination of the dimensions of Jovian 
men would be very pleasing and satisfactory were it not 
that another line of argument guides us at least as con- 
clusively to a very different view. If we are to assume 
that beings resembling men in all attributes except size 
actually exist on Jupiter, we might claim for these beings 
the power of moving from place to place as freely as we 
do, with quite as much reason as Wolfius claimed for 
them the same powers of vision that we possess. Pro- 
ceeding according to this view, we are led to the conclu- 
sion that the Jovicolce are pygmies about two and a half 
feet, on the average, in height. For we know that a man 
removed to Jupiter would weigh about two and a half 
times as much as he does on our own earth. He would 
thus be oppressed with a burden equivalent to half as 
much again as his own weight. This would render life 



JUPITER, GIANT OF TUB SOLAR SYSTEM. 125 

itself an insupportable burden ; and we have to inquire 
what difference of size would suffice to make a Jove-man 
as active as our terrestrial men. Now, the weight of 
bodies similarly proportioned varies as the third power 
of the height ; for example, a body twice as high as an- 
other — in other respects similar — will be eight times as 
heavy. But the muscular power of animals varies as the 
cross-section of corresponding muscles, or obviously as 
the square of the linear dimensions ; so that of two ani- 
mals similarly constituted, but one twice as high as the 
other, the larger would be four times the more powerful. 
He would weigh, however, eight times as much as the 
other. He would therefore be only half as active. Simi- 
larly, an animal three times as high as another of similar 
build, would be only one-third as active ; and so on for 
all such relations. Now, since a terrestrial man removed 
to Jupiter would be two and a half times as heavy as on 
the earth, it follows, obviously, that a man on Jupiter 
proportioned like our terrestrial men would be as active 
as they are, if his height were to theirs as one to two and 
a half. Hence, setting six feet as the maximum ordinary 
height of men on the earth, we see that the tallest and 
handsomest of the Jovicolse can be but about two and 
a half feet in height, if only our premises are correct 
Thus Tom Thumb and other little fellows, if removed 
to Jupiter, might be wondered at for their enormous 
height, and eagerly sought after by any Carlylian Fred- 
ericks who may be forming grenadier corps out yonder. 



126 OTHER WORLDS THAN OURS. 

One line of argument having thus led us to regard the 
Jovicolae as Ogs of Bashan, while another equally plau- 
sible has reduced their dimensions to those of our two- 
year-old children, we may fairly conclude that this method 
of reasoning is fallacious. We must not measure the in- 
habitants of other worlds according to the conceptions 
suggested by the forms of life we are acquainted with 
upon earth. We must admit the possibility that arrange- 
ments as different from those we are familiar with as the 
constitution of the insect is from that of man may be pre- 
sented amid the orbs which circle round the sun. It 
were unwise, no doubt, to give free scope to speculation 
where we have, in truth, no means of forming an opinion. 
We need not imagine, as some have done, that " the in- 
habitants of Jupiter are bat-winged," or, with others, 
" that they are inveterate dancers." Nor to take the 
views of more respectable authorities, need we agree with 
Sir Humphry Davy that the bodies of the Jovians are 
composed of " numerous convolutions of tubes more anal- 
ogous to the trunk of the elephant than anything else ; " 
with Whewell, that they are pulpy, gelatinous creatures, 
living in a dismal world of water and ice with a cindery 
nucleus ; nor finally, with Brewster, that the Jovian may 
have his " home in subterranean cities warmed by central 
fires, or in crystal caves cooled by ocean tides, or may 
float with the Nereids upon the deep, or mount upon 
wings as eagles, or rise upon the pinions of the dove, 
that he may flee away and be at rest " (sic). So soon as 



JUPITER, GIANT OF THE SOLAR SYSTEM. 127 

we give a definite form to the conceptions that the im- 
agination, free from the control of exact knowledge, 
frames respecting the inhabitants of other worlds, we 
touch at once on the grotesque, the hideous, or the ri- 
diculous.* It is sufficient to recognize the probability, 
or rather the certainty, that the beings of other worlds 
are very different from any we are acquainted with, with- 
out endeavoring to give shape and form to fancies that 
have no foundation in fact. 

We may regard it as probable, however, that living 
creatures in Jupiter, if any exist, are built generally on 
a much smaller scale than those which people our earth. 
Trees, plants, and the vegetable world generally, must 
also, one would imagine, be very differently constituted 
from those we are familiar with. It is well known that 
the motion of the vegetable juices is in part regulated by 
the force of gravity, and therefore it must be admitted 
that the structure of terrestrial plants is in part depend- 



* It may be worth while to gather a lesson from this circumstance. 
We know that every form of life is replete with evidences of adaptation 
(no matter how secured) to the conditions which surround it. Now 
man, with all his knowledge of these adaptations, so soon as he passes 
the boundary of the known, pictures to himself all manner of unnatural 
and impossible forms of existence. Even the unknown parts of our own 
earth have been peopled ere now, in imagination, with "men whose 
heads do grow beneath their shoulders." and other similarly incongru- 
ous beings. It is more excusable, perhaps, that an anatomically impos- 
sible structure should have been assigned to angels (the cherubim have 
been even more unfortunate) ; while Satan, who "goeth about as a 
roaring lion," has had the principal attributes of a class of Ruminantia 
assigned to him. 



128 OTHER WORLDS THAN OURS. 

ent upon the value of gravitation at the earth's surface. 
Whewell, in his " Bridgewater Treatise " on the astro- 
nomical evidence of design in creation, lays great stress 
on this relation, pointing out, if I remember aright, that 
all vegetation would be destroyed at once if there could 
suddenly take place any marked change in the earth's at- 
tractive forces. If this view is correct, it is certain that 
none of our plants could thrive on the soil of Jupiter. 

The year of Jupiter differs in a much more striking 
manner than that of Mars from our terrestrial year. It 
consists of nearly twelve such years as ours, so that the 
period corresponding to one of our seasons lasts nearly 
three years, and a Jovian month is nearly equal to one 
of our terrestrial years. He has, however, no seasons in 
our sense of the word, since his equator is inclined but 
little more than three degrees to his orbit. Thus a per- 
petual spring reigns all over his surface. 

But before we proceed to form a high opinion of the 
planet's condition under the influence of this perpetual 
spring, let us distinctly understand what the word means. 
The word " spring " has a genial sound to ourselves, be- 
cause we associate it with that which is commonly the 
pleasantest portion of our year ; but it is just possible 
that the perpetual spring reigning over Jupiter, though 
doubtless well adapted to the wants of his inhabitants, 
leads to a state of things such as we might not find alto- 
gether so agreeable. 

It has been said that " as the rays of the sun fall per- 



JUPITEft, GIANT OF THE SOLAR SYSTEM. 129 

pendicularly on the body of the planet, and always con- 
tinue to do so, the heat must be as nearly as possible 
equal at all times of the year, a perennial summer ; this 
is a striking display of beneficent arrangement." But we 
should be cautious in adopting this mode of argument. 
If Jupiter's great distance from the sun is compensated 
for by this peculiar disposition of his axis, and we are 
to admire the beneficence thus displayed, are we there- 
fore to find maleficence in the fact that Saturn, Uranus, 
and Neptune have been otherwise dealt with, though, be- 
ing further from the sun, they have greater need than 
Jupiter of some special arrangement of the sort ? It 
seems safer to consider the consequences which flow from 
the arrangement without any special reference to its pur- 
pose, lest, in our over-anxiety to recognize beneficence in 
foe treatment of one world, we should adopt a mode of 
reasoning which leads to the direct conclusion that other 
worlds have been ill-treated. 

The great peculiarity resulting from the arrangement 
in question — the only peculiarity, in fact, of which we 
can speak with any confidence — consists in this, that 
everywhere on Jupiter day and night are of equal length. 
It is in this sense only that perpetual spring — or perpet- 
ual autumn, if we please — reigns on the giant planet. 
The different latitudes of Jupiter have climates differing 
quite as much as those found in different latitudes on our 
own earth. At the equator the sun passes every day 
nearly to the point overhead. At the poles the sun seems 



130 OTHER WORLDS THAN OURS. 

to glide along the horizon, rising in the east, passing 
round — always near the horizon — toward the south, and 
thence to his setting-place in the west. In intermediate 
latitudes the sun passes to a southerly elevation, which 
is greater or less according as the place is nearer to or 
further from Jupiter's equator. It follows that there is 
a marked difference between the subequatorial and the 
subpolar regions in Jupiter, while between these regions 
every intermediate climate is to be found. 

Owing to the rapidity of Jupiter's rotation, the motion 
of the sun in the Jovian sky must be much more readily 
discernible and measurable than that with which the sun 
seems to pass across our own heavens. He traverses the 
whole semicircle, from the eastern to the western horizon, 
in two minutes less than five hours, or about six degrees 
in ten minutes. This corresponds to a motion through a 
space equal to the sun's diameter (as we see him) in fifty 
seconds, and must be readily discernible, even to the 
unaided vision of the Jovicolse, unless their eyesight is 
much inferior to ours. The smallness of the sun, as seen 
from Jupiter, must help to render the motion more per- 
ceptible. He presents to them an apparent diameter 
only equal to about one-fifth of that with which we see 
him, so that in ten seconds he seems to pass over a space 
equal to his own diameter. 

The other celestial bodies are affected with similar 
motions as seen from Jupiter. Of course, those seen 
near the poles of his heavens seem relatively at rest. 



JUPITER, 01 ANT OF THE SOLAR SYSTEM. 131 

One of these poles lies in the heart of the constellation 
Draco ; the other lies close by the Greater Magellanic 
Cloud, which must present a magnificent cynosure to the 
inhabitants of the southern hemisphere of the planet. 
The contrast between the steadfastness of the polar star- 
groups and the swift motions of the equatorial constel- 
lations must be impressive indeed. These equatorial 
groups are no other than our old friends the zodiacal 
constellations. As seen by the inhabitants of Jupiter, 
they rise with a perceptible but stately motion above the 
eastern horizon, pass to their culmination on the southern 
meridian, and so to their setting-place in the west — ex- 
hibiting the same splendors which the terrestrial astrono- 
mer delights to gaze upon, enhanced by the peculiar 
impressions of active power suggested by visible and 
obvious motion. 

It may seem, at first sight, that the presence of the 
Jovian satellites must tend to dim the splendor of the 
sidereal heavens. Our own moon, despite the beautiful 
passage * in which Homer has described the calm beauty 
of a moonlit night, certainly detracts largely from the 
magnificence of the star-groups ; and as at times there 
must be four moons visible above the horizon of the 



* Homer must not be held responsible for Pope's amazing descrip- 
tion, which, strangely enough, has found an ardent admirer in one of 
our best modern observers. Homer did, however, mention as a charac- 
teristic of the moonlit sky, that " all the stars shine," a proof that 
sometimes, as Horace tells us, the great master nodded. 



132 OTHER WORLDS THAX 0VR3. 

Jovians, it might seem that all but the brighter stars 
would be quite obliterated. The first moon must appear 
somewhat larger than our own ; the next has an apparent 
diameter rather more than half as large as that of our 
moon ; the third (really the largest) appeals about as 
large as the second ; and the fourth has an apparent 
diameter equal to about a quarter of our moon's. Thus, 
in all, they cover a space on the sky more than half as 
large again as that which our moon covers. But. in real- 
ity, they cannot have nearly so marked an effect in dim- 
ming the lustre of the stars. For it must not be forgot- 
ten that they shin e only by reflecting the sun's light, and 
that he illuminates them but faintly in comparison with 
the light he pours upon our own moon. In effect, sup- 
posing their reflective capacities equal to the moon's, 
they must appeal' less brilliant than she does, in the pro- 
portion of about one to twenty-five ; and,, combining this 
result with the above relation, it follows that even if they 
could all be "full" together, they could send to the 
Jovians but about one-sixteenth part of the light we re- 
ceive from the full moon. But. as a matter of fact, they 
cannot all be full together. The motions of the inner 
three are so related that, though there is nothing to pre- 
vent them from being all visible together,* yet when so 
visible, one only can be full. The fourth may be full at 

* Or all invisible together. Lardner asserts the contrary. One 

would imagine lie had never seen all the moons together on the same 
side of Jupiter. 



JUPITER, GIANT OF THE SOLAR SYSTEM. 133 

the same time, or in fact may be associated with the 
other three in any way, since its motions are not bound 
up with theirs as theirs are inter se. 

Even now, however, we have not reached a full esti- 
mate of the extent of the mistake which those astrono- 
mers have made who speak of the splendor with which 
the satellites of Jupiter illuminate his skies. When at 
that part of their orbits where they would otherwise be 
full, the three inner moons are always eclipsed; and 
though the fourth, by reason of its great distance,* 
sometimes escapes eclipse, yet more frequently it is ob- 
scured like the others. The two inner satellites are 
eclipsed for upward of two hours, and as they occupy 
but a few hours in completing their circuit round the 
nky,f it will be seen how largely this relation detracts 
from their light-supplying powers. 

"We see, then, that those writers have been mistaken 
who allege that the great distance of Jupiter from the 
sun is compensated by the number of his moons, and the 
quantity of light they reflect toward him. So far is this 
from being the case that, under the most favorable cir- 
cumstances, they can supply during the Jovian night but 
about one-twentieth part of the light with which the full 

* Not on account of the inclination of its orbit being large, as has 
been asserted. The orbit of this satellite is, indeed, less inclined than 
the orbits of the others. 

f Moving in a direction contrary to that due to the rotation of 
Jupiter, they of course remain longer above the horizon than the sun, 
or than the equatorial fixed stars. 



134 OTHER WORLDS THAN OURS. 

moon illuminates our nocturnal skies. The poetical de- 
scriptions which imaginative writers have indulged in, 
respecting the splendor of the scene presented by these 
satellites, will not bear the dry light of numerical es- 
timation. That the satellite-system of Jupiter sub- 
serves, or may hereafter subserve, important functions 
need not be questioned ; but that we can recognize 
them as created for any special purpose may be assur j 
edly denied. 

Perhaps, if one were able to discuss with advantage 
the special purposes which this or that portion of the 
universe is intended to subserve, it might be argued that 
the outer planets have greater need of moons than the 
inner, because, their year being longer, there is greate! 
occasion for objects whose motions shall serve as meas- 
ures of time. The satellites of Jupiter supply, by their 
separate motions, convenient measures of the shorter 
time intervals ; while, by their successive conjunctions, 
(1) in pairs, (2) the three inner together, and (3) the 
outer with pairs of the inner, they afford convenient 
measures of longer intervals. 

But let us turn from vague guesses such as these to 
the consideration of those facts which are actually pre- 
sented to our notice. 

Recognizing the existence of varied climatic relations 
in different parts of Jupiter, we have now to consider the 
climate of the planet generally, to contemplate the posi- 
tion of this great orb in the solar system, and to deter- 



JUPITER, GIANT OF THE SOLAR SYSTEM. 135 

mine how far its great distance from the sun may be 
compensated by other relations. 

There can be no doubt that the amount of heat 
poured by the sun on any portion of Jupiter's surface 
placed perpendicularly with respect to the heat-rays, 
must be very much less than the amount received by an 
equal portion of our earth's surface similarly situated. 
The direct heating effects of the sun must in fact, as 
already stated, be less on Jupiter than on our own earth, 
in the proportion of about one to twenty-five. And it 
cannot be doubted that the effects of this difference 
must be highly important, whatever circumstances may 
compensate for the deficiency of heat. If we can demon- 
strate in any way that the mean temperature of the Jo- 
vian atmosphere is equal to that of our own air, or even 
greater, yet the difference of the sun's direct heat in- 
volves a variety of consequences which we cannot disre- 
gard. 

We know, for instance, that it is principally the direct 
heat of the sun that causes the evaporation of water from 
the surface of oceans, seas, lakes, and rivers, and there- 
fore all the important consequences which flow from the 
presence of aqueous vapor in large quantities in the 
earth's atmosphere. We can conceive the existence of 
vapors in the air which might keep away from the earth's 
surface the greater portion of the sun's heat, and yet, 
preventing the escape of the remainder by radiation into 
space, might leave the general warmth of the air around 



136> OTHER WORLDS THAN OURS. 

us as great as it is at present. But it cannot be doubted 
that such an arrangement would injuriously affect the 
whole economy of evaporation and its consequences, 
winds, rains, clouds, mist, with tlieir consequences, so 
important to terrestrial races. 

And in like manner other effects accruing from the 
direct action of the solar rays might be considered. 

It follows, then, that it is by no means sufficient to 
show how the heat which falls upon Jupiter may be 
stored up, through the action of some component of his 
atmosphere in preventing its radiation into space. It is, 
indeed, of the utmost importance to know that even this 
is possible, because we are thus enabled to see that 
Jupiter is not necessarily an abode so bleak and desolate 
as some writers have imagined. In the following pas- 
sage, Professor Tyndall has exhibited the means by 
which this result may be brought about, and the inhabit- 
ants of the noblest planet in the solar system placed 
somewhat higher in the scale of creation than Whewell 
surmised. "In these calculations," he remarked, refer- 
ring to Whewell's estimate of the sun's heating power on) 
Jupiter and the other exterior planets, " the influence of 
an atmospheric envelope was overlooked, and this omis- 
sion vitiated the entire argument. It is perfectly possi- 
ble to find an atmosphere which would act the part of a 
barb to the solar rays, permitting tlieir entrance toward 
the planet, but preventing their withdrawal. For exam- 
ple, a layer of air, two inches in thickness, and saturated 



JUPITER, GIANT OF THE SOLAR SYSTEM. 137 

with the vapor of sulphuric ether, would offer very little 
resistance to the passage of the ether rays, but I find 
that it would cut off fully thirty-five per cent, of the 
planetary radiation. It would require no inordinate 
thickening of the layer of vapor to double this absorp- 
tion; and it is perfectly evident that with a protecting 
envelope of this kind, permitting the heat to enter but 
preventing its escape, a comfortable temperature might 
be obtained on the surface of our most distant planet." 
The difference between such an arrangement as this and 
the way in which the earth's temperature is obtained is 
the exact converse of that dealt with when we were con- 
sidering the case of Mercury and Yenus. Precisely as 
the mean temperature of the atmosphere of either of the 
interior planets may be no higher than that of our own 
air, while yet the sun's direct rays continue wholly un- 
bearable, so the outer planets may have a perfectly com- 
fortable temperature, while yet that direct solar heat 
which exerts so many important influences on the earth 
must be supplied only in quantities which we should find 
wholly inadequate for our wants. 

I am far from desiring to infer that Jupiter may not 
hereafter be uninhabited, or even that creatures then ex- 
isting on his surface must necessarily differ wholly in 
their nature from any with which we are familiar. But I 
think that while, on the one hand, we must reject one of 
the chief arguments by which Whewell was led to people 
Jupiter with cartilaginous and glutinous creatures floating 



138 THER WORLDS THAN OURS. 

in boundless oceans, so, on the other, we cannot accept 
without question the argument by which an effort has 
been made to indicate the possibility of a close corre- 
spondence between Jupiter's climate and our earth's. 

And here we are led to the most interesting and sugges- 
tive of all the relations exhibited by Jupiter, or rather to 
three closely associated relations which lead to views of a 
somewhat startling character. 

In common with the other large planets lying outside 
the zone of the asteroids, Jupiter has a mean density fall- 
ing very far short of the mean density of the earth or the 
other small planets which travel within that zone. Ac- 
cording to the best estimates of his mass and apparent 
diameter, his mean density would seem to be rather less 
than one-fourth of the earth's, or greater than the density 
of water by about one-third. It is worthy of remark, in 
fact, that his density is almost exactly the same as the 
sun's, and considerably greater than that of the other 
three outer planets hitherto discovered. 

If we were quite certain that the disk measured by us 
exhibits the real outline of the planet, or that his atmos- 
phere is not of abnormal extent, and that his globe is 
solid throughout, it would follow that the substances 
composing Jupiter are either altogether different from 
those forming our earth, or that they are combined in 
very different proportions. On the last point we can 
form no opinion. On the first we must be guided by the 
appearance of the planet, 



JUPITER, GIANT OF THE SOLAR SYSTEM. 139 

Thus we are led to the second of the three relations 
just mentioned — the appearance of well-marked but varia- 
ble belts on the planets, and of other indications imply- 
ing the existence of an atmosphere of great depth. 

The belts of Jupiter are commonly arranged with a 
certain symmetry on either side of the great equatorial 
bright belt, but sometimes there is a rather marked con- 
trast between the northern and southern halves of the 
planet. In color the dark belts are usually — when seen 
with suitable telescopic power * — of a coppery, ruddy, 
or even purplish tint, while the intermediate light bands 
vary from a pearly white in the equatorial belt, through 
yellowish-white in the middle latitudes of both hemi- 
spheres, to a grayish or even bluish tint at the poles. The 
picture of Jupiter which forms the frontispiece, while ex- 
hibiting many of the features usually seen, is intended 
specially to illustrate relations presently to be dealt with. 

There is every reason to believe that these belts indi- 
cate the existence of a very extensive vapor-laden atmos- 
phere. The dark belts must not be considered as the true 
cloud-belts, because it must be remembered that we look 



* What is required is not so much a high light-gathering as a high 
magnifying power, though both points are of importance. When the 
light is not adequately reduced by increase of magnifying power, the 
color is lost in the resulting "glare." Reflectors seem to have an ad' 
vantage over refractors in exhibiting the colors of the planets ; at least, 
nearly all the accounts in which the appearance of color has been 
specially dwelt upon have been received from observers who have used 
reflectors,, 



140 OTHER WORLDS THAN OURS. 

upon the reverse side of the skyscape presented during 
the day to the Jovians ; so that where they see densely 
compacted dark clouds, we see the light which those clouds 
have intercepted ; and, on the other hand, where they see 
clear spaces, the light which reaches them is not reflected 
to us without a considerable loss of brilliancy. Thus the 
dark belts of Jupiter are those regions where — if at all — 
we see the true surface of the planet. 

Now, viewing the belts in this light, have we any 
means of judging from their aspect what is the extent of 
the planet's atmosphere ? So far as I know, the question 
has never been considered, but it is well worthy of care- 
ful study. 

It seems clear, in the first place, that if the bright belts 
really are cloud-belts, and the dark belts the surface of 
the planet, then on the edge of the planet's disk we ought 
to see some irregularity of level — the cloud-belts project- 
ing slightly beyond the real outline of the planet — if the 
atmosphere have that enormous extent which some as- 
tronomers have supposed. Whether such an appearance 
has ever been looked for I do not know, but it has cer- 
tainly never yet been detected. 

We are led to conclude, then, that either the atmos- 
phere of Jupiter is not sufficiently extensive to interfere 
appreciably with our measurement of the planet's bulk, or 
else the dark belts belong but to a lower cloud-layer, not 
to the planet's real surface. 

yie have further evidence on this point in the appear- 



JUPITER, GIANT OF THE SOLAR SYSTEM. 141 

luce of dark spots on the dusky belts. These spots have 
ever been described as black, though surely their ap- 
pearing of that hue must be ascribed to the effect of 
contrast. Now these dark spots, which have been seen 
by Cassini, Macller, Schwabe, and others, may be re- 
garded as the real surface of the planet (unless they be- 
long to a yet deeper cloud-layer), seen for a while through 
openings in the cloud-bed to which the dusky belts be- 
long. The reader will not fail to notice here some resem- 
blance to what has been already mentioned respecting 
the sun-spots ; and when we come to the third and most 
striking of the associated features I am now dealing with, 
it will be seen that there may be more in the analogy 
than one might at first sight be disposed to imagine. 

How far the appearance of small, round, white spots 
on the dark belts may be considered as indicative of the 
extent and constitution of the Jovian atmosphere, it is 
not very easy to determine. That they are dense clouds, 
hanging suspended above the dusky cloud-layer, must be 
admitted as highly probable, but it is open to question 
whether they have formed there in the same way that 
cirrus clouds are seen to form at a great elevation above 
a layer of cumulus clouds, or whether they indicate the 
action of volcanoes beneath the dusky layer, propelling 
enormous streams of vapor through the superincumbent 
cloud-beds. 

The third point on which I have to dwell is the vari- 
ability of the belt-system, under which head I include 



142 OTHER WORLDS THAN OURS. 

not only variations in shape and extent, but those much 
more significant changes of color which have been re- 
cently discovered. 

So far as is yet known, there is no recognizable law in 
the changes of shape exhibited by the belts of Jupiter — 
no periodicity or intelligible sequence. It may be sug- 
gested, in passing, that a systematic and persistent scru- 
tiny of the planet might lead to the discovery of laws of 
this sort, which could not fail to indicate physical conclu- 
sions of the utmost importance. Nay, further, since we 
cannot doubt that the condition of the real surface of Ju- 
piter is in some sort reflected, so to speak, in the aspect 
of his cloud-envelopes, it seems far from unlikely that a 
scrutiny of this sort might tell us where his oceans and 
continents, where his deserts, lakes, or rivers, are situ- 
ated, even though no direct evidence of their existence 
might ever reward the observer. In these days, however, 
nine-tenths of those who are fortunate enough to possess 
fine telescopes prefer either to leave them idle, or to em- 
ploy their powers in making observations, at great pains 
and labor, which are not worth the paper on which they 
are recorded. The few original observers we have are 
overtasked by the multitude of questions of interest pre- 
sented to their consideration; so that many subjects of 
inquiry must perforce wait, either till their turn arrives, 
or till those who have the means of studying them choose 
to turn their thoughts from the sterile subjects they are 
now engaged upon. 



JUPITER, GIANT OF THE SOLAR SYSTEM. 143 

So far, then, as inquiries have as yet been pushed, all 
that can be asserted on the subject we are considering is, 
that the planet's belts vary greatly in form, extent, and 
general appearance. At one time the dusky belts cover a 
large proportion of the planet's disk, at another they are 
singularly narrow. Now they are very regularly disposed, 




Fig. 3.— The Planet Jupiter (Browning). 

now they seem in some way under the action of disturb- 
ing forces of great intensity, causing them to assume the 
most irregular figure. The accompanying picture of the 
planet (Fig. 3), as seen by Mr. Browning with one of his 
own reflectors, indicates an appearance not uncommonly 
seen, a dark streak extending obliquely across the planet's 



144 OTHER WORLDS THAN OURS. 

equatorial regions. The number of belts is singularly va- 
riable. Sometimes only one has been seen, at others 
there have been as many as five or six on each side of the 
planet's equator. In the course of a single hour Cassini 
saw a complete new belt form on the planet ; and on De- 
cember 13, 1690, two well-marked belts vanished com- 
pletely, while a third had almost disappeared in the same 
short interval of time. 

The storm-tossed aspect of the planet is well shown in 
the characteristic drawing by Mr. De la Kue, which forms 
the frontispiece. 

But if we seem to recognize here the action of forces 
much more intense than those which influence the condi- 
tions of the earth's atmosphere, we have still more strik- 
ing evidence to the same purpose in the changes of color 
which have recently been detected in the great equatorial 
belt. This belt is usually of a pearly white tint, and has 
long been recognized as one of the most constant features 
of the planet's aspect. As the mean surface of this belt can- 
not be less than a fifth of the whole surface of the planet, 
it is clear that any changes which may take place in its 
general aspect cannot but be of the utmost significance. 
Now, during the autumn of 1869 and the spring of 1870, 
this belt was more strongly colored than any part of the 
planet. Mr. Browning, observing Jupiter in the earlier 
part of the above-named interval, found the equatorial 
belt of a greenish-yellow color, which deepened in Octo- 
ber, 1869, to a full ochreish-yellow, and in January, 1870 3 



JUPITEK, GIANT OF THE SOLAR SYSTEM. 145 

had assumed an even darker tint, resembling yellow 
ochre. On one occasion, and on one only, he detected 
this tint in the first bright belt north of the equator. 
"While thus exhibiting strongly marked and changing 
colors, the equatorial belt had lost its right to be called, 
par excellence, the bright belt of the planet, being consid- 
erably inferior in brilliancy to the narrow bright belts 
north and south of it. 

Other observers have also seen these colors. Mr. 
Slack, with a 6-inch Browning-With reflector, and Mr. 
Brindley, with an 8J-inch telescope of the same construc- 
tion, have witnessed most of the changes of color above 
described; and I myself, using Mr. Browning's 12J- 
inch telescope, found the greenish-yellow tint of the 
equatorial belt in the autumn of 1869 altogether unmis- 
takable. 

In the phenomena here described we have a problem 
whose interpretation is far from easy. Changes in the 
shape, disposition, and extent of the dark belts are suffi- 
ciently intelligible when we associate them, as we seem 
justified in doing, with variations in the position of the 
currents which traverse the vaporous envelope of Jupiter 
as the trades and counter-trades traverse the earth's at- 
mosphere. But the equatorial zone is Jupiter's belt of 
calms, resembling in this respect the equatorial region, 
called by sailors the " doldrums ; " and though occasional 
storms might be expected to agitate this region, yet 

processes of change continuing for several months in 
10 



146 OTHER WORLDS THAN OURS. 

succession can evidently not be attributed to any such 
cause. We are taught by the progress of recent research 
to regard the color of the light derived from any source 
as a relation of the most instructive character ; and 
changes of color, especially changes affecting so enormous 
a body as Jupiter, and so extensive a proportion of his 
surface, cannot but be looked upon as highly significant. 
Supposing we regard the ordinarily white light of the 
equatorial belt as indicative of the existence of enormous 
masses of cloud, reflecting ordinary solar light to us, then 
we should have to regard the appearance of any other 
color over this region as an indication that these cloud- 
masses had been, through some unknown cause, either 
wholly or in part swept away. But — passing over the 
objection that this view leaves our difficulty unexplained 
— even if we assumed that in this way a portion of the 
surface of Jupiter had been brought into view, wholly 
or partially, why should this surface not exhibit a con- 
stant appearance ? We cannot suppose changes affecting 
Jupiter's real surface are taking place with sufficient ra- 
pidity to explain the series of strange color-changes ob- 
served by Messrs. Browning, Slack, and other astrono- 
mers. But if, on the other hand, we assume that a por- 
tion of the light ordinarily received from the bright belt 
is inherent — that is, that the planet is, to some extent, 
self-luminous, then there remains the difficulty of explain- 
ing by what conceivable processes the equatorial regions 
are filled with a yellow light, so full and bright as to 



JUPITER, GIANT OF THE SOLAR SYSTEM. 147 

reach our earth from beyond four hundred millions of 
miles. 

But I have spoken of the three relations last consid- 
ered — the small density of Jupiter, his extensive atmos- 
phere, and the changes which take place in the shape and 
color of his belts — as associated phenomena. It remains 
that I should endeavor to justify this statement. 

We know that Whewell, reasoning from the low specific 
gravity of Jupiter, was led to the conclusion that either 
the substance of the planet is wholly watery or else a few 
cinders in the centre of Jupiter's globe constitute the 
only solid portion of his substance. It need hardly be 
said that the whole progress of modern astronomy is op- 
posed to this view. We have seen that in the sun the 
same elements exist as in the earth; and in Mars, the 
only planet whose nature we have been able to examine 
satisfactorily, we find evidence of the existence of the 
same forms of matter that we see around us. It cannot 
but be held as highly improbable that the earth is the 
only member of the planetary system whose substance 
thus closely resembles that of the parent orb ; nor is it 
likely that Mars is the only planet whose general atmos- 
pheric constitution resembles the earth's. Far more 
probably the lesson we are really to learn from these cir- 
cumstances, is that throughout the solar system a general 
similarity of constitution exists, the sun being, so to 
speak, the type of the family over which he rules. 
Differences of condition we are compelled to recognize, 



148 OTHER WORLDS TBAN OURS. 

since the sun itself, though constituted of the same ele- 
ments as the earth, is in so different a state, and has a 
mean density relatively so small ; but we have no evi- 
dence justifying us in believing that any important differ- 
ences of constitution exist throughout the solar system. 

Thus we are led to regard the singularly small density 
of Jupiter, and of the other planets outside the orbits of 
the asteroids, as due rather to some peculiarity in the 
condition of these orbs than to any such peculiarity oi 
structure as Whewell insisted on. It will be seen at 
once that Jupiter's extensive atmospheric envelope, and 
the strange changes in the aspect of his belts, are circum- 
stances which tend strikingly to confirm this impression. 
Let it be remembered that, supposing Jupiter's globe 
even to be wholly covered with water, yet a sun twenty- 
five times further off than ours could not by any possi- 
bility load the planet's atmosphere with the enormous 
masses of vapor actually present in it. Let it be remem- 
bered, further, that the relatively sluggish action of the 
sun upon Jupiter could not by any possibility give rise 
to atmospheric disturbances so tremendous as those 
which are indicated by the rapid changes of figure of his 
cloud-bands.* When to this we add the relative minute- 



* It is worthy of consideration, also, that even though the sun acted 
as efficiently upon the air and oceans of Jupiter (assumed to be similar 
to our own), yet atmospheric disturbances (due chiefly, as we know, 
to these two fovms of action) could not possibly be so violent even as 
on our own earth, since corresponding latitudes on Jupiter (that is, 
regions where corresponding effects would be experienced) are separated 



JUPITER, GIANT OF THE SOLAR SYSTEM. 149 

ness of the seasonal changes on Jupiter, we see at once 
that unless some other cause than solar action were at 
work, Jupiter's atmosphere ought to be very much calmer 
than the earth's. 

There is yet another circumstance in the condition of 
Jupiter's belts which opposes itself in a very striking (I 
might even say altogether convincing) manner against 
the belief that the belts of Jupiter are raised by the sun's 
action. The tropical cloud-zone of the earth not only 
varies in position with the seasons — passing considerably 
to the north of the equator in summer, and considerably 
to the south in winter — but it is in truth a region of mid- 
day cloudiness, not of general cloudiness. As respects 
the former relation we can learn little from Jupiter's 
aspect, because his inclination is so small that the annual 
sway of his equatorial zone would be exceedingly small 
also, and might well remain undetected. But as the belts 
of Saturn must be regarded as well as those of Jupiter 
in forming an opinion on the subject we are upon, and as 
the chief bright belt of Saturn, despite the considerable 
inclination of the planet's equator, remains throughout 
the year persistently equatorial, we may conclude that 
the Saturnian belts — and presumably, therefore, those of 



by distances so very much greater. It is clear that if along a certain 
zone of a planet the sun exerts a certain amount of influence, while 
along another he exerts a different influence, the result of the differ- 
ence, looked on as a cause of atmospheric disturbance, must be smaller 
as the distance between the zones is greater. 



150 OTHER WORLDS THAN OURS. 

Jupiter also — are not sun-raised. To suppose that the 
sun would have power to raise belts of clouds, and yet 
that he would not have power to cause them to follow 
him as he passes far to the north and to the south of the 
Saturnian equator in the long Saturnian year of twenty- 
nine terrestrial years, seems unreasonable in the extreme. 
It is, however, from the second relation that the most 
direct argument is derived in the case of Jupiter. In the 
latitude of the terrestrial cloud-zone the sun rises in a 
clear sky ; shortly before noon the sky has become over- 
cast, and storms of rain and thunder continue until the 
afternoon is well advanced, after which the clouds pass 
away and the sun sets — as he had risen — in a clear sky. 
Now we know quite certainly that nothing of this sort 
happens in the case of Jupiter ; for we see his equatorial 
bright belt stretching right athwart his disk — that is, not 
only covering the centre of the disk, where it is noon on 
the planet, but extending to the edge on either side, or 
to places where the sun is rising and setting. There 
seems no escape from the conclusion that the belt is 
wholly different in character from our terrestrial cloud- 
belt — that, in fact, it is not sun-raised at all. 

It seems to me that these considerations point with 
tolerable clearness to the conclusion that, within the orb 
which presents so glorious an aspect upon our skies, 
processes of disturbance must be at work wholly different 
from any taking place on our own earth. That enor- 
mous atmospheric envelope is loaded with vaporous 



JUPITER, GIANT OF THE SOLAR SYSTEM. 151 

masses by some influence exerted from beneath its level. 
Those disturbances which take place so frequently and 
so rapidly are signs of the action of forces enormously 
exceeding those which the sun can by any possibility ex- 
ert upon so distant a globe. And if analogy is to be our 
guide, and we are to judge of the condition of Jupiter 
according to what we know or guess of the past condition 
of the earth and the present condition of the sun, we 
seem led to the conclusion that Jupiter is still a glow- 
ing mass, fluid probably throughout, still bubbling and 
seething with the intensity of the primeval fires, sending 
up continually enormous masses of cloud to be gathered 
into bands under the influence of the swift rotation of 
the giant planet. No otherwise, as it seems to me, can 
one explain the intense vitality, if I may use the expres- 
sion, of a planet circumstanced as Jupiter is. No other- 
wise can one understand whence his atmosphere is loaded 
with vapor-masses whose contents must exceed, on a 
moderate computation, all the oceans on the surface of 
this earth. When we see masses so enormous swayed 
by influence of such energy that intermediate belts thou- 
sands of miles in width are closed up in a single hour,* 
when we recognize the tremendous character of the mo- 
tions which from beyond four hundred millions of miles 



* Even if we take the disappearance of a dark belt to be due to the 
formation of clouds, which is perhaps more probable than that the 
clouds of neighboring belts have closed in, the forces represented by 
the change are nevertheless tremendous. 



152 OTHER WORLDS THAN OXTRS. 

are distinctly cognizable by onr telescopes, we see that 
we have no ordinary phenomena to deal with, and that 
the theory we adopt for their explanation cannot be 
otherwise than striking and surprising. 

If the view which I have here put forward — or rather, 
lite view to which I have been led by a careful consider- 
ation of the phenomena which Jupiter presents to our 
contemplation — be indeed correct, we must of course dis- 
miss the idea that the giant planet is at present a fit 
abode for living creatures. Yet need we not turn from 
his system with the thought that here at least our hopes 
of recognizing other worlds have been disappointed. If 
Jupiter be still in a sense a sun, not indeed resplendent 
like the great centre of the planetary scheme, but still a 
source of heat, is there not excellent reason for believing 
that the system which circles around him consists of four 
worlds where life — even such forms of life as we are fa- 
miliar with — may still exist? Those four orbs, which 
our telescopes reveal to us as tiny points of light, are in 
reality globes which may be compared with the four 
worlds that circle nearest to the sun. I have shown that 
they cannot subserve the purpose which many astrono- 
mers have ascribed to them, of compensating Jupiter for 
the small amount of light he receives, even if they could 
be seen from any point of his cloud-encompassed surface. 
So that, even adopting the commonplace and superficial 
view that the purpose of any object may be regarded as 
ascertained when we have been able to ask (without any 



JUPITER, GIANT OF THE SOLAR SYSTEM. 153 

obvious answer) what other purpose it can subserve, we 
still are led to the belief that the satellites of Jupiter 
must be the abode of life, since on this view, and on this 
view only, we find a raison d'etre both for the planet and 
for the system which circles round him. 

There are no considerations which appear directly op- 
posed to the view that Jupiter is in a sense a sun. It 
need hardly be said that I do not regard him as being in 
the same condition as the central luminary of the plan- 
etary system. If he is an incandescent body, the greater 
part of his light is veiled by the cloud-envelopes which 
surround him. The solar clouds are, as we know, them- 
selves luminous ; those of Jupiter are not so — a circum- 
stance which indicates that the heat of Jupiter is not 
sufficient to vaporize those substances which are incan- 
descent when in the liquid state. The outer layer of 
clouds must, therefore, be regarded as for the most part 
aqueous. "We see there, in fact, the future oceans of 
Jupiter, if the hypothesis I am now dealing with be cor- 
rect. 

That Jupiter may supply an immense amount of heat 
to his satellites (on this view of his condition) is per- 
fectly clear, since the amount of light he emits is no 
adequate measure of the amount of obscure heat which 
radiates from him to the four worlds around him. When 
we consider the enormous apparent size of Jupiter as 
seen from his satellites, we recognize at once how large a 
supply of heat he is capable of transmitting to them. 



154: OTHER WORLDS THAN OURS. 

From the outermost satellite his apparent diameter ex- 
ceeds that of the sun (as seen by us) some eightfold, and 
his apparent size, therefore, exceeds the sun's more than 
sixtyfold. From the innermost he is seen with a diame- 
ter nearly forty times that of the sun, and with an ap- 
parent area more than 1,400 times as large as his ! 

We have evidence, however, which renders it far from 
improbable that Jupiter may emit some small proportion 
of light. I have already referred to the singular excess 
of his brilliancy over that due to his size and his dis- 
tance from the sun and from us. The estimates of 
Zollner, the eminent photometrician, serve to show, not 
indeed that Jupiter sends more light to us than he re- 
ceives from the sun, but that he sends much more light 
than a planet of equal size, and, constituted like Mars, 
the moon, or the earth, could possibly reflect to us if 
placed where Jupiter is. Whereas Mars reflects but one- 
fourth of the light he receives, Jupiter reflects more 
than three-fifths. The moon sends less than a fifth ; 
Saturn, Jupiter's brother giant, more than a half. The 
late Professor G. Bond, of America, actually calculated 
that Jupiter sends forth more light than he receives. 
Whether his observations or the more systematic obser- 
vations of the German astronomer are accepted, we see 
that unless we adopt some such hypothesis as I have 
dealt with above, we must recognize a marked difference 
between the relative light-reflecting capacities of the two 
largest planets of the system, and those of Mars or the 



JUPITER, GIANT OF THE SOLAR SYSTEM. 155 

moon. In fact, from other researches of Dr. Zollner's, it 
follows that if Jupiter does not shine in part by native 
light, his surface must possess reflective powers nearly 
equal to those of white paper. Now this would scarcely 
be credible, even though under the telescope the planet's 
surface were found to be uniformly white; but as we 
find a large proportion of it to be of a dull coppery hue, 
we seem forced to admit that it cannot really have an 
average reflective power nearly so great as that calculated 
by Zollner. It follows, as at least highly probable, that 
Jupiter shines in part by his own light ; and this being 
admitted, we cannot but regard it as highly probable 
that the real globe of the planet must be intensely hot. 

It may seem, at first sight, that the apparent blackness 
of the satellites' shadows, as seen on the disk of Jupiter, 
is wholly opposed to the view that any portion of his 
light is native. But as a matter of fact there is no force 
at all in this consideration, or rather, whatever weight 
we may attach to the observed appearance of the satel- 
lites' shadows is in favor of the strange theory here put 
forward. For it has been a subject of remark among the 
most experienced observers, that a satellite in transit will 
oceasionally appear as dark as its shadow, both seeming 
black. The blackness, then, is only apparent, and an 
effect of contrast. In reality, if such observations as I 
have mentioned are to be trusted (and I know no reason 
for disregarding them), the shadow of a satellite is not 
black, and therefore there seems no escape from the con- 



156 OTHER WORLDS THAN OURS. 

elusion that the surface on which they are projected is 
partially self-luminous. 

A stronger argument against the belief that Jupiter is 
self-luminous lies in the fact that the satellites disappear 
in his shadow. It must be remembered, however, that 
in any case we can assign but a small proportion of in- 
herent light to Jupiter, and that his satellites would 
therefore, in any case, lose so large a proportion of their 
light when passing into his shadow that we might expect 
them to disappear, even under the closest telescopic 
scrutiny. 

One of the most surprising phenomena ever witnessed 
by the telescopist seems to me to afford even stronger 
evidence than any yet adduced. I refer to the observa- 
tion made by Admiral Smyth, that on one occasion the 
second satellite of Jupiter, twelve minutes after entering 
on the disk of the planet, was seen outside the limb, 
" where it remained four minutes, and then suddenly 
vanished." Two other equally competent observers, 
Maclear and Pearson, witnessed the same phenomenon. 
" Here," says "Webb, " explanation is set at defiance." 
But it is precisely where explanation seems at defiance 
that we have reason to be most hopeful of gaining in- 
struction. The observation is very startling, it is true ; 
and the explanation may be expected to be also surpris- 
ing. But I think it is not far to seek. The satellite 
cannot have retraced its course ; Jupiter cannot have 
shifted his place ; our atmosphere cannot be in question ; 



JTJPITEB, GIANT OF THE SOLAR SYSTEM. 157 

all these explanations being eliminated, our task is ren- 
dered easier instead of more difficult. A change in 
Jupiter's cloud-laden atmosphere, corresponding to that 
which I shall presently have to exhibit as explaining 
Saturn's occasional assumption of the square-shouldered 
aspect, will obviously account for the phenomenon. It is 
well known that the acute observer Schroter occasionally 
suspected an apparent flattening of portions of Jupiter's 
outline, but the suspicion had been regarded as erro- 
neous. We find, however, in the observation now in 
question, effective confirmation of that long-doubted 
observation of Schroter's. If we consider the matter 
rightly, this observation, made simultaneously by Smyth, 
Maclear, and Pearson, renders that view all but certain 
which hitherto I have presented only as a highly prob- 
able hypothesis. 

Although I have already far exceeded the limits I had 
proposed to myself for the consideration of this noble 
planet, it is with regret that I take leave of him to pass 
onward to the outermost bounds of the solar system. I 
would fain dwell even longer than I have on a subject 
of contemplation at once so interesting and so instructive. 
Jupiter, the centre of a noble system of worlds, or Jupi- 
ter, himself a world inhabited by beings as high perhaps 
in the scale of creation as he himself is in the scheme 
of the planets, is alike a worthy subject of study. The 
more one dwells on the features he presents, the more one 
is impressed with the sense of the grandeur of his position 



158 OTHER WORLDS THAN OURS. 

in the universe. One who has not gazed hour after hour 
on the glories of the giant planet, gathering fresh delight 
as feature after feature is revealed beneath his scrutiny, 
may disregard the grand lesson which the heavens are 
always teaching. But the astronomer, imbued with the 
sense of beauty and perfection which each fresh hour of 
world-study instills more deeply into his soul, reads a 
nobler lesson in the skies. The music which reaches his 
ears may be fitful, but it is not " as sweet bells jangled 
out of tune and harsh ; " he may not master its full 
meaning, though every note thrill through his inmost 
soul ; but even when its sounds are least distinct, they 
are full of mystical solemnity. In fine, the true astrono- 
mer may say with the Pythagorean, though in another 
sense — 

There's not one orb which thou behold'st 
But in his motion like an angel sings, 
Still quiring to the young-eyed cherubim ; 
But while this muddy vesture of decay 
Doth grossly close us in, we cannot hear. 



SATURN, TEE RINGED WORLD. 159 



CHAPTER VI. 

SATURN, THE RINGED WORLD. 

If Jupiter by his commanding proportions affords a 
forcible argument against the view that our tiny earth is 
the only real world in the solar system, Saturn supplies 
an argument of scarcely inferior strength in the singularly 
complex character of the scheme of which he is the cen- 
tre. No one can contemplate this glorious planet, as 
shown by a telescope of adequate power, without being 
impressed by the conviction that he is looking at a world 
altogether more important in the scheme of creation than 
the globe on which we live. Whether he recognizes in 
the present condition of the planet the result of the action 
of laws which have for vast periods reigned through the 
universe, or whether he prefers the view that Saturn and 
his system are seen now as they were fashioned at the be- 
ginning by an Almighty creative hand, he is alike amazed 
at the complexity of structure exhibited in the scene on 
which he is gazing. He may not be able, indeed, to ap- 
preciate the true character of the life-work which the va- 
rious parts of the Satumian system are doing, or he may, 
in a too hasty attempt to solve the mighty problem, be 
led to erroneous conceptions ; but that the great planet 



160 OTHER WORLDS THAN OURS. 

speaks of life, past, present, or to come, he cannot gravely 
question.* 

In volume and mass Saturn is inferior to Jupiter. Ju- 
piter is 1,230 times, Saturn not quite 700 times, as large 
as the earth ; and while Jupiter outweighs her 300 times, 
Saturn is scarcely 90 times as heavy as she is. Still Sat- 
urn is sufficiently large and massive to dwarf our earth 
to insignificance ; and even Uranus and Neptune, though 
belonging to the family of the major planets, and giants 
compared with the earth, fall below Saturn far more than 
he does below Jupiter. 

Like Jupiter, Saturn rotates very rapidly on his axis, 
the length of his day being about 10J of our hours. The 
materials of which Saturn is composed have a mean 
density not much greater than half that of Jupiter, or 
less than three-fourths of the mean density of water. In 
fact, Saturn's mean density is specifically less than that of 
any known planet. It seems not impossible that we have 
in this relation some indication of the true cause of that 
complexity of detail which the Saturnian system exhibits. 

The equator of Saturn is inclined about 28-J- degrees to 
the plane in which the planet moves, so that his seasons 
(so far as they depend on this circumstance) closely re- 
semble in character those of the planet Mars. He occu- 

* I know nothing better calculated to lead men to choose astronomy 
as their favorite subject of study than the contemplation of the Satur- 
nian system. I can well remember the sensations with which I saw 
the ringed planet for the first time. I look on that view as my intro- 
duction to the most fascinating of all the sciences. 



8ATUHN, THE RINGED WOULD. 161 

pies about 29£ years in circling once round the sun ; this, 
therefore, is the length of the Saturnian year. His dis- 
tance from the sun is nearly twice that of Jupiter, and 
nearly ten times that of the earth ; so that the amount of 
light and heat which any portion of his surface receives 
from the sun is about -^ T part of that received by a similar 
portion of the earth's surface. His orbit being somewhat 
eccentric, however, there is a considerable variation in 
this respect during the course of a Saturnian year, inso- 
much that when he is nearest to the sun he receives more 
light that when in aphelion, in the proportion of about 5 
to 4. 

Most of the relations which have to be considered in 
discussing the habitability of Saturn have been already 
dealt with (under very similiar conditions) in treating of 
other planets ; so that I propose to touch on them very 
lightly, in order to come more quickly to those circum- 
stances which distinguish Saturn specially among the 
other members of the solar system. 

Gravity at his equator is almost exactly equal to gravity 
at the earth's surface. Near the poles there is a marked 
increase in the action of Saturnian gravity, insomuch that 
a body weighing 10 pounds at his equator would weigh 
about 12 pounds at either pole. There is nothing, how- 
ever, in this peculiarity which need be specially dwelt 
upon. 

The length of the Saturnian year, and the small quan- 
tity of light and heat received from the sun, are simply 
11 



102 OTHEK WORLDS THAN OURS. 

more marked instances of what has already been consid- 
ered in the case of Jupiter. We may conclude with some 
confidence that these relations are quite sufficient to 
render Saturn wholly uninhabitable by such creatures as 
exist upon the earth ; but there seems no reason for sup- 
posing that (so far as these relations alone are concerned) 
the planet may not be the abode of living beings as high 
in the scale of creation as any which live upon our globe. 

In viewing Saturn, we cannot regard even the excep- 
tional effects produced by his ring-system as of them- 
selves sufficient to banish life from his surface. These 
effects are not without interest, however, and as they have 
been made the subject of some discussion, I think it well 
to make a few remarks upon them. 

I apprehend that when Sir John Herschel said that the 
rings occasion an eclipse of nearly fifteen years in dura- 
tion, first to the northern and then to the southern hemi- 
sphere of the planet, he meant simply that during an in- 
terval of such length a large portion of either hemisphere 
was in shadow. He knew perfectly well that long after 
the edge of the ling has been turned directly toward the 
sun, a very large proportion of the hemisphere over which 
the ring's shadow proceeds to sweep remains illuminated. 
It had always seemed to me, therefore, altogether a mis- 
take on the part of Dr. Lardner to interpret Herschel's 
words as though implying that a whole hemisphere of the 
planet is eclipsed for fifteen years in succession. 

So misinterpreting the expression used by Sir John 



SATURN, THE RINGED WORLD. 163 

Herschel, Dr. Lardner, in his desire to show that no such 
relation existed, was led into real mistakes such as a 
sounder mathematician would not have made. He ex- 
amined the relations presented by the ring in a quasu 
mathematical but inexact manner, and came to the follow^ 
ing conclusion — "that by the apparent motions of the 
heavens produced by the diurnal rotation of Saturn, the 
celestial objects, including the sun and the eight satellites, 
are not carried parallel to the edges of the rings ; that 
they are moved so as to pass alternately from side to side 
of these edges ; that, in general, such objects as pass 
under the rings are only occulted by them for short inter- 
vals before and after their meridional culmination ; that 
although, under some rare and exceptional circumstances 
and conditions, certain objects — the sun being among the 
number — are occulted from rising to setting, the endur- 
ance of these phenomena is not such as has been sup- 
posed, and the places of their occurrence are far more 
limited." All these statements are more or less incorrect, 
and most of them are the direct reverse of the truth. 
The seven inner satellites of Saturn stand in an altogether 
different relation with respect to the rings from all other 
celestial objects, since they travel in the same plane and 
in circles concentric with the outlines of the rings : they 
can no more be occulted by the rings, therefore, than an 
outer ring can be occulted by an inner one. So far is it, 
again, from being true that the sun is in general only 
occulted for a short time before and after culmination, 



164 OTHER WORLDS THAN OtfM. 

that the more common case (considering the whole planet) 
is for the sun to be eclipsed (if at all) throughout the 
whole of the Saturnian day ; and a very common case, left 
altogether unnoticed by Dr. Lardner, is that the sun is 
occulted in the forenoon and afternoon, but free from 
eclipse in the middle of the day. Nor is it true that the 
places where the sun can be totally eclipsed throughout 
the day are limited to a relatively small portion of the 
planet, since every part of the planet whence the rings are 
visible at all has the sun eclipsed by the rings through- 
out the whole day for a longer or shorter succession of 
rotations. In the remaining or polar regions of the planet 
the sun is altogether absent for long intervals of time, for 
the same reason that he is absent from the skies of our 
polar regions during a comparatively short interval. As 
for the endurance of the total diurnal eclipses, it is only 
necessary to remark that in the Saturnian latitude cor- 
responding to that of London or Paris the sun is totally 
eclipsed for more than five years in succession, while in 
the latitude corresponding to that of Madrid he is totally 
eclipsed for nearly seven years in succession. This suf- 
fices to show that an arrangement which the inhabitants 
of earth would find wholly unendurable prevails over a 
very large proportion of Saturn's surface.* 



* The views here expressed as to the effects of the Saturnian rings 
are founded on exact mathematical calculation, of which the elements 
are given in my treatise on Saturn; The problem is not by any means 
A difficult one, and the only way in which the erroneous views formed 



SATURN, THE RINGED WORLD. 165 

But if we consider the matter rightly, we shall see that 
this, after all, need not surprise us, since there is already 
in the enormous distance of Saturn from the sun the 
amplest reason for believing that he cannot be inhabited 
by such creatures as exist upon the earth. It is in vain 
that by conceiving him to be surrounded by a dense 
atmosphere we assign to him a mean climate as warm as 
that of the earth. The want of direct solar heat still 
remains, and must be regarded as a fatal objection to the 
habitability of Saturn by races resembling those with 
which we are familiar. 

In the case of Saturn as in the case of Jupiter, the 
provision of satellites and of the rings which form so 
glorious an object to the astronomer on earth is altogether 
inadequate to increase the supply of light received by the 
Saturnians to any such extent as has been imagined. 
Those well-meaning persons who insist on their own 
interpretation of Deity's designs are singularly success- 
ful in overlooking very obvious difficulties. If the design 
of the rings, for instance, really were to compensate the 
Saturnians for the small amount of light which they re- 
ceive from the sun, it would surely follow that there was 



by Dr. Lardner can be explained is by considering that he dealt with 
the problem in a general instead of an exact manner. I could not feel 
any doubt as to the accuracy of my results, but I was not the less pleased 
to receive a letter from Mr. Freeman, a fellow of St. John's College, 
Cambridge, stating that he had obtained similar results, and had con- 
structed a table on the plan of Table XI. in my Saturn, and so closely 
according with it as not to need separate publication. 



166 OTHER WORLDS THAN OURS. 

a want of wisdom in the selection of an arrangement by 
which more light is kept away from Saturn than the rings 
can possibly reflect to him. And, further, during the 
very season when the extra light derived from the rings 
is most required by the planet, that is, during the long 
nights of the Saturnian winter, they exhibit a dark band 
upon the heavens, concealing whole constellations from 
the view of the Saturnian people. As far as the satellites 
are concerned there is no corresponding difficulty. They 
undoubtedly reflect the sun's light to Saturn, and if there 
really are intelligent beings on the planet, the satellites 
must undoubtedly present an interesting spectacle, es- 
pecially when a large number of the moons are nearly 
full. But a little consideration will show that even though 
all the satellites were full at the same time, the quantity 
of light they could send back to their primary would be 
wholly inadequate to compensate for the planet's great 
distance from the sun. According to the best estimates 
of their magnitude, the eight satellites,, taken in their 
order from their planet, cover spaces on the Saturnian 
heavens which bear to the space covered by our moon the 
respective proportions of about 2, 1, 1J, f , f , -§-, T ^ ¥ , -£$. 
In all, then, they cover an area about six times that of our 
moon ; and as, owing to their great distance from the sun, 
they are illumined by only T ^th of the light which illu- 
minates our moon, they could only send back to the 
planet, if it were possible for them to be all full together, 
about yV^h P ai> t °f ^ ne light we receive from the full 



SATURN, THE RINGED WORLD. 16? 

moon. It will be remembered that the light which 
would be reflected from the Jovian moons, if they could 
be all full together, bears about the same proportion to 
our moon's. We seem forced to the conclusion that the 
satellites were not intended to subserve any such design 
as has been imagined. Here, as in many other cases, the 
scheme of creation is not so obvious to human reasoning 
as some have complacently supposed. 

But we have now to consider peculiarities which suggest 
that Saturn's globe has not yet reached a condition fitting 
it to be the abode of living creatures. These peculiarities 
resemble in great part those which have been already 
noticed in the case of Jupiter, but a certain most remark- 
able phenomenon belongs to the ringed planet alone. 

The belts of Saturn resemble those of Jupiter in their 
general shape (see Fig. 4) and also in their color. The 
dark belts near the equator are of a faint brown or ruddy 
tinge, those near the pole bluish or greenish gray, while 
the bright belts are yellowish — the equatorial belt being 
the brightest of all, and almost white. The poles are 
commonly dusky, and even sombre in hue. 

The belts change in aspect much as those of Jupiter 
have been observed to do ; and whether we regard the 
change as due to the bodily transference of the belts of 
cloud or to the precipitation of their material in the form 
of rain (while, elsewhere, invisible vapors are condensed 
into clouds), we are compelled to recognize the action of 
forces altogether exceeding those which the sun can be 



168 OTHER WORLDS THAN OURS. 

supposed to exert upon this distant planet. The light 
sent to us from Saturn also bears a much greater propor- 
tion to the amount of solar light actually received by the 
planet than is observed in the case of Mars or the moon, 
and so nearly approaches the proportion noticed in the 
case of Jupiter as to lead to the same inference — namely, 
that a portion of Saturn's light is emitted from the body 
of the planet. 

In these respects, and also in the small density of the 
planet, we seem to recognize evidence which points to 
Saturn as probably a heat-sun (if not to any very note- 
worthy extent a light-sun) to the satellites which circle 
around him, and not himself the abode of living creatures. 
"Without dwelling further on evidence already fully con- 
sidered in the case of Jupiter, I turn to one of the most 
striking facts in the whole range of observational astron- 
omy, as supplying at once new evidence respecting the 
condition of Saturn, and strengthening the evidence ad- 
duced respecting Jupiter. 

If it can be shown that Saturn's globe is subject to 
changes of figure perceptible even across the enormous 
gap which separates him from the earth, it will at once be 
admitted that he can hardly be regarded as a globe con- 
veniently habitable. Now I have very little hesitation 
in saying that evidence of the most conclusive kind exists 
in favor of this strange mobility of figure. It will pres- 
ently be seen that it is with the observations of no mere 
amateur astronomers that I have to deal in endeavoring 



SATURN, TEE RINGED WORLD. 169 

to establish, as a fact that which has commonly been 
spoken of as an' illusion — the assumption by Saturn of his 
so-called " square-shouldered " figure. 

It was in April, 1805, that Sir William Herschel first 
called attention to this peculiarity. The planet, which 
had always presented to him an elliptical figure, exhib- 
ited a strangely distorted aspect. A well-marked flat- 
tening at the equator, accompanied by an equally well- 
marked flattening at the poles, gave the planet's globe an 
oblong figure (with rounded angles), the longest diameters 
having their extremities in Saturnian latitude 48° 20' — so 
exactly was the great astronomer able to indicate the nat- 
ure of the deformity, owing to its well-marked character. 

What view shall we form respecting an observation of 
so remarkable a nature ? Was the peculiarity due to tele- 
scopic distortion ? Herschel observed it with several in- 
struments, some seven, some ten, one twenty, and one 
forty feet in length. Was the phenomenon due to atmos- 
pheric disturbances? Such disturbances could not ac- 
count for a persistent impression, however well they 
might explain the momentary assumption of the square- 
shouldered aspect by the ringed planet. Besides, Jupiter 
presented no such appearance. Was the appearance an 
optical illusion, due to the position of the ring — then 
slightly open? If so, the planet should always exhibit 
the square-shouldered aspect when his rings are open to 
that particular extent ; and this is not the case. Besides, 
we ought to notice a similar illusion when looking at a 



170 OTHER WORLDS THAN OURS. 

picture representing that particular phase of Saturn. 
Must we then accept the astounding conclusion that the 
giant bulk of Saturn is subject to throes of so tremendous 
a nature as to upheave whole zones of his surface five or 
six hundred miles above their ordinary level ? Truly the 
conclusion is one to be avoided, if we can by any possi- 
bility find a less startling explanation of the matter. 

Yet where are we to look for such an explanation? 
Was Sir William Herschel simply deceived? I have 
already considered the general question of illusion, but 
the reader might entertain the explanation as conceivable 
that Herschel had for a while lost the acumen which dis- 
tinguished him — that illness, for example, might have 
rendered his observations inexact. But we have abun- 
dant evidence that the great astronomer was in the full 
possession of all his wonderful powers as an observer 
during the month of April, 1805 ; we know further that, 
by careful measurements, he rigidly excluded all possi- 
bility of illusion affecting his judgment. 

It would be more satisfactory, doubtless, to the reader, 
however, to learn that other observers had noticed simi- 
lar peculiarities, or peculiarities which, if not similar, 
were at least such as to prepare us to consider the globe 
of Saturn liable to remarkable changes of figure. Fortu- 
nately many such observations have been recorded. I 
take the following from one of a lengthy series of papers 
on Saturn by Mr. Webb in the Intellectual Observer for 
1866, 



SATURN, THE RINGED WORLD. 171 

On August 5, 1803, Schroter found Saturn not per- 
fectly spheroidal in figure. Kitchener says that for a 
few months in the autumn of 1818 he saw Saturn of the 
figure described by Sir William Herschel, and that with 
two different achromatics. At this time the ring must 
have appeared too narrow to account for the appearance 
as due to illusion. On one occasion Sir George Airy 
had a similar view of Saturn. He remarks, also, that a 
person unacquainted with Herschel's observation re- 
marked spontaneously on the flattened equator of the 
planet. On another occasion, Sir George Airy noticed 
the exact reverse, the planet seeming flattened, instead 
of upheaved, in latitude 45°. In January, 1855, Cool- 
idge, using the splendid refractor of the Cambridge 
(U. S.) Observatory, noticed that the greatest diameter 
of the globe seemed inclined about 20° to the equatorial 
diameter ; but on the 9th the equatorial diameter seemed 
the greatest ; while on December 6th he says : "I cannot 
persuade myself that it is an optical illusion which makes 
the maximum diameter of the ball intersect the limb half- 
way between the northern edge of the equatorial belt and 
the inner ellipse of the inner bright ring." All this time 
the rings were nearly at their greatest opening, so that 
any illusion should have been of an opposite character to 
that observed when the rings were nearly closed. In 
the report of the Greenwich Observatory for 1860-61 it 
is stated that " Saturn has sometimes appeared to exhibit 
the square-shouldered aspect." The eminent observers 



172 OTHER WORLDS THAN OURS. 

Bond, father and son, have noticed similar peculiarities, 
using the great Merz refractor already referred to. Each 
of them noticed a flattening of the north-polar regions of 
the planet in the summer of 1848, when the ring was 
turned edgewise toward us. On the other hand, the 
same observers noticed that in 1855-57, when the ring 
was most widely opened, the polar region did not always 
seem projected furthest on the outer ring in a symmetri- 
cal manner, but four times on the left of the pole, once 
on the right, and once only exactly opposite the pole. 
" The outline of this region, also, occasionally appeared 
irregularly flattened and distorted," an appearance not 
satisfactorily explained by the juxtaposition of the dark 
shadow of the planet on the ring. 

Now there can be no doubt whatever that the planet 
Saturn is not ordinarily distorted. In 1832, during the 
disappearance of the ring, Bessel carefully determined 
the figure of the planet's disk, and Main in 1848 (when 
the ring was again turned edgewise toward us) made 
similar measurements. Each of these trustworthy au- 
thorities came to the conclusion that the disk of Saturn 
did not, at the seasons when they respectively measured 
it, exhibit any distortion of figure such as Herschel had 
described. 

We seem almost compelled, therefore, to accept the 
conclusion that the planet Saturn is subject to the influ- 
ence of forces which either upheave portions of its sur- 
face from time to time, or cause vast masses of cloud to 



SATURN, THE RINGED WORLD. 173 

rise to an enormous height above the mean level of Sat- 
urn's cloud-envelope. Whichever view we adopt, we can- 
not fail to recognize the fact that an intense heat must in 
all probability prevail in the great globe of Saturn ; and 
doubtless the real mass of the planet must emit a brill- 
iant light, though the cloud-strata surrounding him may 
prevent us from recognizing more than a minute propor- 
tion of his luminosity. In fact, according to this view, 
Saturn and Jupiter, unlike the sun, whose real sub- 
stance emits a less intense light than the cloud photo- 
sphere surrounding him, must have nuclei — solid or liq- 
uid — shining with an altogether more brilliant light 
than the cloud-envelopes of these planets seem actually 
to emit. 

Why Saturn, rather than Jupiter, should exhibit from 
time to time these mysterious changes of figure is readily 
explicable when we remember that the plane in which 
the Jovian satellites move nearly coincides with the or- 
bital plane of their primary. There thus always results a 
close agreement between the zone on which the satellites 
exert their greatest disturbing influences and that most 
influenced by the solar action. No such coincidence ex- 
ists in the case of Saturn, whose satellites travel in a 
plane inclined nearly 30 degrees to that in which their 
primary travels. We have seen, however, that evidence 
is not wanting to prove that Jupiter is really liable to 
occasional changes of figure, though not to such an ex- 
tent as to change the general aspect of the planet. 



174 OTHER WORLDS THAN OURS. 

I think the evidence in the case of Saturn favors, at 
least as strongly as that which has been adduced in the 
case of Jupiter, the belief that the giant planets outside 
the zone of asteroids are not themselves suitable abodes 
for living creatures, but are suns, supplementing the small 
amount of light, and yet more fully supplementing the 
small amount of heat which the sun supplies to the satel- 
lites circling around these orbs. Undoubtedly, if we are 
to judge according to the method which has been so often 
applied to such questions, if we are to ask ourselves ac- 
cording to what arrangement the central planets and the 
systems circling round them seem most reasonably inter- 
preted, we should at once adopt some such conclusion. 
For, by taking Jupiter and Saturn to be strictly analogous 
to our own earth, and their satellites to be subsidiary 
bodies, resembling our moon in this, that they subserve 
at present no other purpose but to illuminate the noc- 
turnal skies, and to sway the oceans of their primaries, 
we find ourselves perplexed by the consideration that a 
much simpler arrangement would have subserved these 
purposes much more completely. In the case of Saturn's 
satellites, indeed, it seems difficult to conceive that these 
bodies could have been intended to fulfil any such pur- 
poses, since the two outer ones could neither give any 
useful light to their primary, nor sway appreciably any 
oceans which may exist upon the planet. 

These considerations lead me to believe that the two 
most important members of the planetary scheme must 



SATURN, THE RINGED WORLD. 175 

be left without inhabitants for the present, while in ex- 
change I submit, to the contemplation of the curious, 
twelve small orbs, constituting two miniature world- 
systems. The condition of these worlds will be touched 
on briefly in a separate chapter. 



176 OTHER WORLDS THAN OURS. 



CHAPTEE Vn. 

TJBANUS AND NEPTUNE, THE AECTIC PLANETS. 

A circumstance which is of great importance in consid- 
ering the relations of the outer planets is apt to be lost 
sight of, owing to the unsatisfactory manner in which in 
nearly all books on astronomy the planetary orbits are 
represented. To look at the series of equidistant and 
concentric circles representing the orbits of the planets, 
who would suppose that in passing from the orbit of Ju- 
piter to that of Saturn a distance five times as great as 
that which separates our earth from the sun has to be 
traversed ? But the distance separating Uranus from Sat- 
urn is twice as great even as this tremendous gap, while 
Neptune travels as far beyond Uranus as Uranus beyond 
Saturn. Nine hundred millions of miles in width is the 
enormous gap by which the path of Uranus is separated 
from that of the ringed planet on the inner side, and 
from that of distant Neptune on the outer ; so that a line 
equal to the diameter of Jupiter's orbit would barely suf- 
fice to reach from Saturn to Uranus, or from Uranus to 
Neptune, even when either pair of planets are in con- 
junction. 

We know so little of the physical aspect of Uranus and 



URANUS AND NEPTUNE, THE ARCTIC PLANETS. 177 

Neptune that it is extremely difficult to form any opinion 
as to their condition. The two planets resemble each 
other in size, each being far smaller than either of the 
giant orbs we have lately been considering. Uranus has 
a diameter of about 33,250 miles ; Neptune is somewhat 
larger, his diameter having been estimated at 37,250 
miles. The volume of Uranus is 74, the volume of Nep- 
tune 105 times that of the earth. Both planets exceed 
Saturn in density ; for whereas Saturn's mean specific 
gravity* is but y^ths, that of Uranus is T y ¥ ths, and that 
of Neptune iV 6 o^ ns °f ^ ne mean specific gravity of our 
globe. Thus each planet has a density nearly equal to 
that of water. The mass of Uranus exceeds the earth's 
about 12^ times, while that of Neptune is some 16f times 
as great as the earth's. It will be seen, therefore, that 
though these two far-distant worlds are much less mas- 
sive than Jupiter or Saturn, each of them outweighs many 
times the combined mass of the four planets which travel 
within the zone of asteroids. Yet gravity on the surface 
of these two orbs is but about three-fourths of terrestrial 
gravity. 

The disk of the sun as seen from Uranus is less than 
that which we see, in the proportion of 1 to nearly 390, 
while the Neptunians have a sun only about -g^-g-th °^ ours 
in apparent size ; and in these proportions the solar light 
and heat received by these planets are respectively di- 
minished. So small does the sun appear, in fact, that to 

eyes such as ours his orb would not present a disk-like 
12 



178 OTHER WORLDS THAN OURS. 

figure, but would appear like an exceedingly brilliant 
day-star. 

So far we have found the circumstances of the two plan- 
ets somewhat similar. But we have now to consider a 
relation presented by Uranus, which is not shared in by 
Neptune. It may be remarked that we know so little 
about either planet that any very careful consideration of 
their habitability would be simply a waste of labor. The 
evidence I am about to adduce, however, in the case of 
Uranus, seems thorougly to dispose of the claim of this 
planet to be regarded as a world inhabited by creatures 
resembling those we are acquainted with on earth ; and as 
we cannot reasonably suppose Neptune to be inhabited 
by such creatures while Uranus is not, we may very fairly 
regard the question as disposed of for both planets, even 
though the relation dealt with is peculiar to Uranus. 

Uranus has a family of four satellites, Neptune has 
only one satellite yet discovered. Now we know that in 
the case of Jupiter, as in that of Saturn, the position of 
the plane near which the satellites travel is nearly coinci- 
dent with the plane of the primary's equator. Therefore, 
though no telescope has yet exhibited any features on 
the disks of Uranus or Neptune which can enable us to 
determine the position of its equator, we can safely infer 
from the motion of the satellites how the equators of the 
planets are situated. 

Now the satellites of Uranus travel in a plane very 
nearly at right angles to the plane in which the planet 



URANUS AND NEPTUNE, THE ARCTIC PLANETS. 179 

travels. It may be mentioned also, though not important 
for my present purpose, that they travel in a retrograde 
direction. The satellite of Neptune travels in a path not 
inclined more than about 27° to the plane of the planet's 
path ; but the motion of the satellite is retrograde. We 
conclude that the axis of Uranus lies very nearly in the 
plane wherein the planet moves around the sun, and that 
the planet rotates in such a way around this axis that the 
sun moves across the Uranian skies from west to east, in- 
stead of from east to west. The latter relation is of no 
great importance ; the former, however, involves results 
which dispose at once, and thoroughly, of any hopes we 
might entertain of discovering creatures in Uranus re- 
sembling those which inhabit the earth. 

The inclination of the plane of Uranus' equator to the 
path in which he travels being about 76°, it follows that 
the Uranian sun has a range of about 76° on either side 
of the celestial equator, during the long Uranian year. 
Already, in considering the seasons of Yenus, I have 
dealt with a peculiarity of this sort ; but in the case of 
Uranus the effects are more serious. "We have only to 
consider what would be the result of so wide a range of 
solar excursion north and south of the celestial equator in 
a latitude corresponding to that of London, to see how 
importantly the climatic relations of a planet like Uranus, 
occupying eighty-four years in circling once round the 
sun, must be affected by such a peculiarity. We know 
that in the latitude of London the sun reaches at noon, in 



ISO OTBEn WOBLDS THAN OUMS. 

spring or autumn, an elevation of about 38£° above the 
southern horizon, that in summer he passes the meridian 
23£° higher, while in winter he passes the meridian 23^° 
lower, or only 15° above the horizon. But in a similar 
Uranian latitude, while the sun would reach the same 
meridian elevation in spring or autumn, he would in sum- 
mer travel throughout the day in a small circle, 14° only 
from the pole (raised of course 51^° above the horizon), 
so that at noon he would be 65|°, and at nominal mid- 
night 37^° above the northern horizon. And obviously, 
since the year of the Uranians lasts eighty-four of our 
years, the continuance of the sun above the horizon would 
last for many years.* So far there is nothing to render 
life in Uranus unpleasant, always supposing the small 
amount of light and heat supplied by the sun to be com- 
pensated by some such atmospheric arrangements as phys- 
icists have thought necessary for the convenience of the 
more distant planets. But when we consider the nature 
of the Uranian winter, we find the circumstances such as 
no arrangements of the sort can be conceived to alleviate. 
The winter path of the Uranian sun, in a latitude corre- 
sponding to that of London, is just as fully depressed 



* Exact calculation applied to relations so uncertain as those here in 
question would be out of place. From a careful construction, however, 
with 76' as the assumed value of the inclination of the equator of 
Uranus to the plane of his orbit, I find that the sun would continue 
above his horizon in summer for about 23 J years. Of course it follows 
that the sun would continue below the horizon for an equally long 
period in winter I 



VPANVS AND NEPTUNE, THE ARCTIC PLANETS. 181 

below the horizon as the summer path is raised above it. 
At midnight the sun is 65^°, at nominal noon he is 37£ c 
below the southern horizon. And as with the summer 
day, so with the winter night, years elapse before either 
comes to an end. For upward of twenty years, in a lati- 
tude corresponding to that of London, the Uranians — if 
there are any — never see the small Uranian sun. During 
all this long time, too, a sight even is denied them of all 
parts of the solar system interior to the orbit of Uranus ; 
though this deprivation cannot be regarded as very serious 
when it is remembered that to such eyesight as ours Sat- 
urn would barely be visible from Uranus, even when most 
favorably situated, while Jupiter, always near the sun, 
would only be occasionally seen, shining with a light 
somewhat less than a fiftieth of that which he reflects to 
us when in opposition. 

When we consider other latitudes, we find Uranus ill 
provided for as respects his winter season. In all lati- 
tudes nearer the pole than the latitude just considered, 
the Uranians have winters lasting from twenty years to 
upward of forty. In latitudes nearer the equator the 
winter night is shorter, but we must approach quite close 
to the equator before we reach a latitude where the winter 
night lasts less than a year or so. Over a belt extending 
about 14° on each side of the equator there is a perennial 
succession of days and nights never exceeding the full 
duration of the Uranian diurnal rotation. But we must 
not suppose that we have thus found an Elysian zone in 



182 OTHER WORLDS THAN OURS. 

Uranus. The immense range of the sun's excursions pro* 
duces here also a variety of seasonal changes which we 
should find altogether unendurable. From a sun barely 
rising above the horizon in winter, to a sun which rises 
vertically overhead twice in the course of the Uranian 
summer, is a change which hardly accords with our views 
of what is desirable in the progress of the seasons. At 
the equator itself there are in reality two summers, oc- 
curring at the period of the sun's passing the celestial 
equator. Here for many years together the sun passes 
day after day to a point nearly overhead. But then 
comes the long winter, in the heart of which the sun rises 
barely 14° above the northern or southern horizon. By 
whatever arrangement we render the long Uranian winters 
in this part of the planet endurable, we render the heat 
of his long summers unbearable; and vice versd, if we 
conceive of atmospheric relations which would render his 
summers pleasing, we have caused his winters to be so 
intensely cold that no creatures we are familiar with could 
endure the prolonged and bitter frosts, contrasting so 
distressingly with the imagined geniality of his summer 
weather. 

If Uranus be inhabited at all, then, it must be by 
creatures constituted in a very different manner from 
any with which we are acquainted. To such creatures,. 
if any among them be gifted with intelligence, the 
heavens, though not adorned with planets, must yet 
present an interesting subject of study. The position 



URANUS AND NEPTUNE, THE ARCTIC PLANETS. 183 

of the pole, lying close by the zodiac, so that among 
the zodiacal constellations there are all the varieties of 
motion which we recognize in passing from the equato- 
rial to polar constellations, would lead to a certain com- 
plexity in celestial charts and globes, which would invite 
us to the conclusion that the Uranians must be capital 
mathematicians. Then there are certain astronomical 
subjects of study to which their mathematical powers 
may be devoted perhaps more successfully than those of 
our astronomers. For example, the wide sweep of the 
planet's orbit would enable the Uranians to recognize a 
displacement of the stars in the course of the long "[Iran- 
ian year. The star Alpha Centauri, which only exhibits 
to the terrestrial observer an annual parallax of one 
second, would exhibit to the observer on Uranus a dis- 
placement of about the third part of a minute. Other 
stars would be affected in like proportion, and perhaps 
the Uranians may thus be enabled to form some concep- 
tion of that relation which hitherto has proved too 
baffling a problem to our astronomers — the actual config- 
uration of the nearer parts of the sidereal system. The 
Neptunians would of course be even more favorably cir- 
cumstanced. 

One difficulty presents itself, however, in thus consid- 
ering the prospects of the Uranian and Neptunian 
astronomers. The enormous length of the year of each 
planet requires that either the astronomers in Uranus 
and Neptune should be very long-lived, or that they 



184: OTHER WORLDS THAN OURS. 

should be very enthusiastic in the cause of science, to 
prosecute singly such observations as Henderson, Olbers, 
or Peters have singly prosecuted on our earth. A 
Uranian who made one set of observations to determine 
stellar parallax when he was, say, twenty-five years old, 
would have to wait till he had nearly reached the 
three-score years and ten (not perhaps allotted as the 
span of Uranian life) before he could make the corre- 
sponding set, by comparing which with the former stellar 
parallax was to be determined. In Neptune life must be 
prolonged over the century (unless the study of obser- 
vational astronomy commence during the babyhood of 
the Neptunians), in order that a complete set of observa- 
tions for determining stellar parallax should be carried 
out. One cannot but conceive that a certain sluggish- 
ness would mark the progress of astronomy in these far- 
off worlds under such circumstances. In fact, the mere 
consideration that after a constellation has passed away 
from the nocturnal skies of Uranus or Neptune, thirty or 
forty years in one case and seventy or eighty in the 
other must pass before the constellation again becomes 
favorably visible, suggests characteristics of astronomical 
observation altogether different from those we are familiar 
with. 

Admiral Smyth suggests that these distant planets 
must be convenient outposts for watching the approach 
or recession of comets ; but I venture to point out that 
the inhabitants of the earth are on the whole more favor- 



URANUS AND NEPTUNE, THE ARCTIC PLANETS. 185 

ably situated in this respect. Every large comet which 
approaches tolerably near to the sun during perihelion 
passage is as likely to be seen as to be missed by the in- 
habitants of earth ; but scarcely one out of a thousand 
such comets would be seen from Uranus or Neptune, 
since to be visible a comet must approach the sun 01 
recede from him along a course passing tolerably near to 
the particular position of either planet at the time ; and 
the changes in the case of any individual comet would be 
enormously against such a contingency. 

With eyesight such as ours the Uranians would dis- 
tinctly see Neptune when in opposition, but the Neptun- 
ians would be wholly unable to see Uranus, or indeed any 
known planet of the solar system. 

Perhaps, though we have very little evidence on the 
point, it will be thought more reasonable to suppose that 
Uranus and Neptune are suns to their respective systems 
of satellites, than to imagine that these two drearily cir- 
cumstanced planets are themselves inhabited. Their sat j 
ellites cannot possibly compensate to any noteworthy ex- 
tent for the small amount of solar light or heat which 
reaches their primaries. On the other hand, it is not 
difficult to conceive that the planets may afford an im- 
portant supply of heat (at any rate) to their depen- 
dent orbs. Certainly, so far as the evidence we have ex- 
tends, Uranus and Neptune resemble Saturn and Jupiter 
too closely not to warrant the application of any argu- 
ments deduced from the appearance of the two giant 



186 OTHER WORLDS THAN OURS. 

planets to the case of their inferior but still gigantic 
brethren. 

Viewing the matter thus, we seem led to the conclusion 
that the planets which lie outside the zone of asteroids 
are distinguished from those within that belt, not merely, 
as had so long been recognized, by the attributes of size, 
density, rapidity of rotation, and the complexity of sys- 
tems circling round them, but in this more important and 
more interesting circumstance, that they and their de- 
pendent orbs are real miniatures of the solar system. 
Four suns they would seem to be, not indeed suns re- 
splendent like the primary sun round which they travel, 
yet giving out perhaps no insignificant supply of light ; 
not heated to incandescence as he is, but still supplying 
an amount of heat proportionately far greater than the 
quantity of light they give forth : in fine, not, as he is to 
the inner planets, the sole source whence all supplies of 
force are derived, but adding their influence to his in a 
variety of complicated but doubtless well-ordered combi- 
nations, in such sort that the small worlds which circle 
around them are provided with all that is necessary for 
the well-being of their inhabitants. 



THE MOON AND OTHER SATELLITES. 187 



CHAPTEE Vffl. 

THE MOON AND OTHER SATELLITES. 

Although the moon cannot be regarded as at present 
the abode of any forms of life, such as we are familiar 
with on earth, there are many reasons for studying in a 
work on other worlds the various relations she presents 
to us. In the first place, she subserves various useful 
purposes in the economy of our own earth ; then there 
are circumstances in her appearance which suggest that 
at one time there may have been life upon her surface ; 
and lastly, she affords us the only information we have 
concerning the probable relations presented by the noble 
systems of moons which circle around Jupiter and the 
other planets outside the zone of asteroids. 

With regard to the present habitability of the moon, 
it may be remarked that we are not justified in asserting 
positively that no life exists upon her surface. Life has 
been found under conditions so strange — we have been 
so often mistaken in assuming that here certainly, or 
there, no living creatures can possibly exist — that it 
would be rash indeed to dogmatize respecting the state 
of the moon in this respect. 

Still, in the case of the moon we have relations wholly 



188 OTHER WORLDS THAN OURS. 

different in character from those we have hitherto had 
to consider. We no longer have to deal with various de- 
grees of heat and cold, of atmospheric rarity or density, 
and the like, but with relations which do not in the slight- 
est degree resemble those we are familiar with on earth. 

In the first place, the moon has no appreciable atmos- 
phere. We have long known this quite certainly, be- 
cause we see that when stars are occulted by the moon 
they disappear instantly, whereas we know this would 
not be the case had the moon an atmosphere of appre- 
ciable extent. But if any doubt could have remained, 
the evidence of the spectroscope in Mr. Huggins' hands 
would have sufficed to remove it. He has never been 
able to detect a sign of the existence of any lunar atmos- 
phere, though Mars and Jupiter, so much farther from 
us, have afforded distinct evidence respecting the atmos- 
pheres which surround them. 

Then secondly, there are no seas or oceans on the 
moon. Were there any large tracts of water, the tre- 
mendous heat to which the moon is subjected during the 
course of the long lunar day (lasting a fortnight of our 
time) would certainly cause enormous quantities of 
water to evaporate ; and not only would the effects of 
this process be distinctly recognizable in the telescope, 
but the spectroscope would exhibit in an unmistakable 
manner the presence of the aqueous vapor thus formed. 

Thirdly, there are no lunar seasons. The inclination 
of the moon's axis to the orbit in which she travels 



THE MOON AND OTHER SATELLITES. 189 

round the sun is nearly 89°, and with this inclination 
there can be no appreciable seasonal changes. 

Fourthly, the enormous length of the lunar day is 
altogether opposed to our conceptions of what is suitable 
for animal or vegetable life. The lunar day lasts about 
a, fortnight, and the lunar night is, of course, equally 
long. Were this all, the inconvenience of the arrange- 
ment would not be endurable by beings like ourselves. 
But far more serious consequences must result from the 
combination of the arrangement with the want of an at- 
mosphere ; for whereas during the lunar day the surface 
of the moon is exposed to an inconceivably intense direct 
heat, undoubtedly sufficient to heat that surface far above 
the boiling-point, during the lunar night the heat is 
radiated rapidly away into space (no atmosphere check- 
ing the process), and an intensity of cold must prevail of 
which we can form but imperfect conceptions.* 

The mere fact that our earth is always invisible from 



* The moon's physical habitudes are in fact so very different from 
those of the earth that one cannot read without astonishment the fol- 
lowing passage in which Sir W. Herschel pleads for the moon's habita- 
bility. "Its situation, with respect to the sun," he says, "is much 
like that-of the earth, and hy a rotation on its axis it enjoys an agree- 
able variety of seasons (!) and of day and night. To the moon, our 
globe will appear to be a very capital satellite, undergoing the same 
regular changes of illumination as the moon does to the earth. The 
sun, the planets, and the starry constellations of the heavens will rise 
and set there as they do here, and heavy bodies will fall on the moon 
as they do on the earth. There seems only to be icanting, in order to 
complete the analogy, that it slwuld be inhabited like the earth!" The 
evidence however, seems to me to lie all the other waj. 



190 OTHER WORLDS THAN OURS. 

three-sevenths of the moon's surface is one which points 
very strongly to the conclusion that the present condition 
of the moon is not the one best calculated to meet the 
wants of living creatures on her surface. In long-past 
ages, when her rotation had not yet been forced into ac- 
cordance with her revolution * (as at present), the earth 
must have subserved a variety of most important pur- 
poses. If water then existed on the surface of the moon, 
the earth must have raised tidal waves in the lunar 
oceans. She must further have reflected enormous sup- 
plies of light and heat toward her dependent orb, even if 
at that time she were not a secondary sun for the lunari- 
ans. She must have travelled across the lunar skies as 
the moon travels over ours, presenting a variety of inter- 
esting and beautiful phases, affording useful time-meas- 
ures, and so enabling the travellers on the moon in 
those long-past ages to guide their course in safety over 
her oceans or her deserts. But now she is invisible from 

* The researches of Adams into the peculiarity of the moon's motion 
called her acceleration, suffice to show that under the influence of the 
moon's attraction on our oceans, the earth's rotation is gradually dimin- 
ishing ; so that, though many millions of ages must elapse first, she 
will one day so rotate as to keep always the same face turned toward 
her satellite. We cannot doubt that it has been by a process of this 
sort that the moon's rotation has been brought to its present rate. In 
fact, independently of the evidence afforded by the earth's gradual 
loss of rotation, we cannot account for the moon's peculiarity of rota- 
tion without regarding it as due to the earth's controlling influence. A 
perfectly homogeneous sphere, started on a direct line at the moon's 
distance, and with the same velocity, would travel without rotation on 
an orbit like the moon's, and would thus in completing a revolutioa 
exhibit every part of its surface to us. 



THE MOON AND OTHER SATELLITES. 191 

a large portion of the moon's surface, and almost a fix- 
ture in the skies even of those parts of the moon whence 
she can be seen. Were there lunar oceans, she could 
raise no tides in them. Were there a lunar atmosphere, 
she could shed no heat, to be garnered up, so to speak, 
by that atmosphere, and to compensate, in some sort, 
for the long absence of the sun. 

But have we evidence that at some far-distant epoch 
the moon was inhabited ? Taking for our guidance the 
analogies which are available to us, can we really con- 
clude that once, in all probability, those barren wastes 
were clothed with vegetation, those dreary solitudes the 
abode of life ? 

When we contemplate with attention the lunar surface, 
considering the indications it presents of past activities, 
we are led to inquire how the forces which have been 
so busily at work were expended. If Nature, studied 
thoughtfully, teaches us the lesson that there is no form 
of force which is not the representative of some other 
pre-acting form of force, she also teaches us that no form 
of force ever works without generating other forces as its 
own energies are expended. The meteor which sweeps 
with planetary velocity through space may be brought to 
rest upon the sun, but the energy stored up in its mo- 
tions is not wasted; the sun may expend the stores of 
force he derives from meteoric impact, but not idly;* 

* The question may be asked, What becomes of the immense supplies 
of light and heat continually poured by the sun and other stars into 



192 OTHER WORLDS THAN OURS. 

all round us we see the fruits of solar energies, we feel 
them within ourselves, we exert them upon others. And 
therefore when we see on the moon signs that her sur- 
face was at one time upheaved by tremendous volcanic 
forces, we are led to the conclusion that between the era 
when she was thus disturbed, and the present time, 
when she seems absolutely quiescent, there must have 
been a period when her energies were fit for sustaining 
various forms of life; though it does not follow, of 
course, that they were so employed. There lias, in this 
instance, been a process resembling exhaustion, though 
we know that the forms of force which have passed away 
from the moon have not really ceased to exist ; but be- 
fore the lunar forces were dissipated into space, they may 
have subserved the purpose of supporting life. 

space ? We cannot tell ; yet we know certainly that they cannot be 
wasted. The heat of Arcturus, measured by Mr. Stone, gives an ac- 
count of one large portion of the stellar heat supplies, because we know 
that, small as the amount may be, we must multiply that amount mill- 
ions on millions of times to get the total received by all the orbs in 
space from this particular sun. But we know that a large portion of 
our sun's light and heat must either fail to fall on any other orbs, or 
must be gradually exhausted in its progress through space (for if lines 
from the sun in every direction encountered orbs, the sky ought to be 
lighted up at all times with star splendor — which is no other than sun- 
splendor). In either case we cannot tell what becomes of the portion 
seemingly wasted ; though in the latter case we may affirm confidently 
that there is simply a change in the nature of the energy. In both 
cases we know that the total of energy in the universe remains undi- 
minished. There is, indeed, a seeming contradiction here ; but it is 
not different in character from the seeming contradictions suggested by 
the consideration of infinite space and infinite time, which yet we are 
compelled to recognize as absolutely as finite space or finite time. 



TUB MOON AND OTHER SATELLITES. 193 

Associated, however, with, this subject, there are ques- 
tions of a perplexing character, which invite our careful 
consideration. If life ever existed on the moon, she 
must have possessed an atmosphere and seas. Indepen- 
dently, also, of our views on the subject of life upon the 
moon, we are led by the revelations of the spectroscope 
respecting the solar system, to believe that all the bodies 
within that system are in a general sense similarly con- 
stituted; and if this be so, there must once have been 
oceans and air upon the moon. "What has become of the 
moon's atmospheric envelope, and of the lunar oceans ? 

In four several ways this question has been answered. 
Some have thought that the oceans and air have been 
withdrawn into cavities within the moon's substance. 
Others have imagined that the air and oceans may have 
passed away to the farther hemisphere of the moon. 
According to a third theory, a comet has carried off the 
lunar oceans and atmosphere. And lastly, a fourth theory 
has been maintained, according to which the lunar air, 
and a fortiori the lunar seas, have been changed by in- 
tensity of cold into the solid form. 

Of these theories, the first and last only seem worthy 
of consideration. "We see so much of the moon's farther 
hemisphere during her librations that we must perforce 
reject the second, even if we had any trustworthy reason 
for believing so strange an arrangement to be possible.* 



* Professor Newcomb, of America, has shown excellent reasons for 
doubting whether even that displacement of the moon's cenire of grav* 
13 



194 OTHER WORLDS THAN OURS. 

The third theory is opposed by all that modern astron- 
omy teaches respecting the constitution of comets. 

The theory that an atmosphere formerly surrounding 
the moon has passed with the lunar oceans into the in- 
terior of our satellite has been supported by physicists of 
considerable eminence. The relatively low specific gravity 
of the moon (little more than half the earth's) suggests the 
possibility that cavities large enough to contain even all 
the waters of our own oceans may exist within the moon. 
Nor does the fact that we can see no unmistakable signs 
of chasms extending deep into the moon's substance 
suffice to render the theory untenable, or even improbable. 
It is difficult to understand how the retreat of the waters 
took place. Certainly it cannot have happened while the 
moon's volcanic forces were in vigorous action; yet a 
period must undoubtedly have arrived when by little and 
little the waters could retire within the moon's substance 
without being vaporized. From what we know of volcanic 
action on the earth, the lunar volcanoes must have drawn 
fresh supplies of energy from the gradual influx of water ; 
and one can thus understand why the aspect of the moon 
indicates that up to the last moment, so to speak, of her 



ity, on which the theory has been based, can be admitted as an estab- 
lished fact. Independently of this, however, the theory will not bear 
close examination. Any one who will draw a cross-section of the moon 
(in a plane passing through the earth), and endeavor to assign such a 
position to an atmosphere of moderate extent that even during the 
moon's extreme librations no signs of the atmosphere would be per- 
ceptible from the earth, will at once see that the theory is untenable. 



THE MOON AND OTHER SATELLITES. 195 

existence as a world, the forces upheaving her crust were 
busily at work. We can thus see how it has come to pass 
that the moon's surface shows so few signs of the action 
of rain or running water. 

The theory that the lunar oceans have become frozen, 
and that afterward even the gases forming the lunar 
atmosphere have become solidified, was maintained by 
Buffbn and Bailly in the last century, and has been sup- 
ported by several astronomers in our own day. In some 
respects, the aspect of the moon (especially the absence 
of well-marked colors from her surface) seems to favor 
the theory. Nor need the excessive heat, to which the 
moon's surface is exposed for weeks at a time, be con- 
sidered a sufficient reason for rejecting it, because we 
have no means of judging how that heat would act where 
there is no atmosphere to prevent its immediate and entire 
reflection into space. "We know that despite the intense 
heat which is poured upon the summits of the Hima- 
layas, the snow there — though a portion may melt during 
the day — remains year after year and age after age undi- 
minished ; and on the summit of the Himalayas the 
atmosphere is dense and heavy compared with that which 
exists even in the lowest abysms of the lunar ravines. 
But the results which have been deduced from the ap- 
plication of Lord Rosse's three-foot mirror to the measure- 
ment of the lunar heat, compel us to abandon the belief 
in the existence of frozen oxygen or nitrogen on the 
moon's surface, since, according to those results, a lasge 



19$ OTBER WORLDS THAN OtTMS. 

proportion of the moon's heat is radiant — in other words, 
the xaoon's surface has been actually raised to a high 
degree of heat by the solar rays. Most physicists look 
with considerable confidence on the method by which, in 
the researches made at Parsonstown, an attempt has been 
made to distinguish between the heat which the moon re- 
flects and that which she radiates into space. 

On the whole, therefore, the former theory seems to 
have the strongest evidence in its favor, or rather the 
least decisive evidence against it. 

In considering the systems of bodies which circle around 
the outer planets, we are struck at once by several marked 
circumstances of contrast between their condition and 
that of our own moon. 

In the first place, we have no satisfactory evidence that 
the satellites of Jupiter and Saturn turn always the same 
face toward their primary. It is true that Sir William 
Herschel was led by certain observations of the satellites 
of Jupiter to conclude that this relation holds in their 
case. But we have far stronger evidence against such 
a view, in the fact that modern observers armed with 
telescopes of the most exquisite defining powers have not 
only been unable to confirm the relatively rough observa- 
tions made by Herschel, but have noticed peculiarities of 
appearance only explicable by the theory that the rota- 
tion of the satellites is quite independent of their motion 
of revolution around Jupiter. Dawes, for instance, has 
observed that the markings seen on the third satellite, 



THE MOON AJSTD OTHER SATELLITES. 197 

when transiting Jupiter's disk, are variable. Bond has 
seen this satellite as a well-defined black spot on certain 
occasions, while on others it has appeared quite bright on 
the disk of the planet. He once saw this satellite bright 
as it entered on the disk • of Jupiter, and about half an 
hour later as a dark spot ; while Mr. Prince, with a 
powerful reflector, has seen the satellite dark first and 
afterward bright. It need hardly be said, that if the 
satellite turned always the same face toward its primary 
no such varieties of appearance would be presented dur- 
ing transit! The following passage from Webb's "Ce- 
lestial Objects " points strongly also to the conclusion 
that the rotation .of the Jovian satellites must be inde- 
pendent of their revolution. After mentioning that the 
variable light of the satellites may be caused by the ex- 
istence of spots upon their surface, he proceeds : "A 
stranger source of anomaly has been perceived — the disks 
themselves do not always appear of the same size or form. 
Maraldi noticed the former fact in 1707, Herschel ninety 
years afterward inferring also the latter, and both have 
since been confirmed. Beer and Madler, Lassell and 
Secchi, have sometimes seen the disk of the second satel- 
lite larger than that of the first ; and Lassell, and Secchi 
and his assistant have distinctly seen that of the third 
satellite irregular and elliptical ; while, according to the 
Boman observers, the ellipse does not always lie the same 
way." 
It will easily be seen that these peculiarities indicate the 



198 OTHER WORLDS THAN OURS. 

existence of dark markings on these bodies, and that, as 
the satellites rotate, the varying position of these mark- 
ings causes the satellites seemingly to change in figure, 
since the brighter part of the satellite would be that 
which would determine its apparent figure. And fur- 
ther, since the change of figure shows no correspon- 
dence with the position of the satellites in their revolu- 
tion, we infer that their revolution is independent of their 
rotation. 

It is worthy of notice, however, that even if the inner 
satellites turned always the same face toward their pri- 
mary, the peculiarity would not (as in the case of our 
moon) result in an inordinate lengthening of their diurnal 
period, since Jupiter's two inner satellites complete a 
revolution in 1 day 18£ hours, and 3 days 13 hours re- 
spectively; while the revolutions of Saturn's five innet 
satellites are severally accomplished in 22 \ hours, 1 day 9 
hours, 1 day 21 hours, 2 days 18 hours, and 4 days 12^ 
hours. 

So far as we can judge from Laplace's estimates, the 
specific gravity of Jupiter's moons must be very small, 
ranging from one-third to two-thirds of the moon's specific 
gravity. But very little reliance can be placed on these 
results, because the only evidence we have respecting the 
mass of the satellites is that founded on the perturbations 
to which their motions are subjected, and it is very diffi- 
cult indeed to estimate these perturbations. When to 
this we add the circumstance that little reliance can be 



THE MOON AND OTHER SATELLITES. 199 

placed on measurements of the minute disk presented by 
the satellites, it will be seen that our estimate of the 
specific gravities of these bodies cannot by any means be 
regarded as trustworthy. 

As seen from his satellites, Jupiter must present a mag- 
nificent scene. To the inhabitants, if such there are, of 
the innermost satellite, he exhibits a disk nearly 20° in 
diameter. Thus, whereas there might be about seven 
hundred moons such as ours placed all around our horizon, 
fche disk of Jupiter, as seen from the inner satellite, would 
occupy a full eighteenth part of the horizon's circumfer- 
ence. The disk of Jupiter, as so seen, would cover a 
space on the heavens exceeding more than fourteen hun- 
dred times that which our moon covers. To the second 
satellite, Jupiter presents a disk about 12J a in diameter, 
or about six hundred times as large as our moon's. To 
the third satellite he shows a disk about 7|° in diameter, 
or more than two hundred times the size of the moon's. 
And lastly, the inhabitants even of the farthermost satel- 
lite see him with a diameter of about 4£° — that is, with a 
disk more than sixty-five times as large as that of our 
moon. So that, if the views I have put forward respect- 
ing Jupiter be correct, the enormous space he covers on 
the skies of his respective satellites must suffice to com- 
pensate in part for the relatively small amount of heat 
which he can be supposed capable of emitting. 

If the satellites rotate with a motion independent of 
their revolution, Jupiter passes across their skies like a 



200 OTHER WORLDS THAN OURS. 

vast moon, exhibiting phases such as those presented by 
ours, but on a far vaster scale. But besides his phases, 
he must exhibit to the inhabitants of his satellites the 
most marvellous picture that can be conceived. His belts' 
changes of figure and color, only rendered visible to our 
astronomers by powerful telescopic aid, must be distinctly 
visible to creatures on his satellites, and cannot but afford 
reasoning beings on those orbs a most astounding theme 
for study and admiration. 

To the inhabitants of the satellites which circle round 
Saturn, the ringed planet must present an even more in- 
teresting spectacle. His disk as seen from the nearest of 
his satellites has a diameter of 17° and an apparent sur- 
face exceeding more than nine hundred times that of the 
moon. From the farthest satellite his disk is less than a 
degree in diameter, and therefore not quite four times as 
large as our moon's. Between these limits the apparent 
size of Saturn varies as we pass from satellite to satellite ; 
but from the sixth satellite his apparent surface is twenty- 
five times, while from the seventh it is sixteen times as 
large as the moon's; so that the outer satellite is quite 
exceptionally circumstanced in this respect. 

It is not so much from the apparent size of his disk, 
however (though in the case of all the inner satellites that 
must be a most remarkable relation), as from the peculiar 
character of his ring-system, that Saturn would derive 
his chief interest. It is true that the inner satellites 
travel nearly in the plane of the rings, so that these are 



THE MOON AND OTHER SATELLITES. 201 

always presented nearly edgewise. But even so viewed, 
the rings would present a most striking appearance. 
From the inner satellite, indeed, the extreme span of the 
ring-system is more than 90° ; * so that when one ex- 
tremity is seen on the horizon the system would appear 
as an arch thickest in the middle, extending over an arc 
of about 93°, and having the disk of Saturn at its centre. 
When the whole of this arch is illuminated, Saturn is 
" full ; " at other times he presents all the phases shown 
by our moon, and the arch of light is correspondingly 
shortened. Saturn " full " and in the zenith, with the 
ring-system dependent on either side of his disk, must be 
a glorious spectacle as seen from certain regions of his 
innermost satellite. The display would diminish in 
grandeur, though not perhaps in interest, as seen from 
satellites farther and farther away. But the inhabitants 
of the outermost satellite of all have the privilege of see- 
ing the Saturnian ring-system opened out much more 
fully than as seen from the other satellites, since the path 
of this moon is inclined some 15° to the plane of the 
ring. 

Of the satellites of Uranus and Neptune little can be 
said, because so little is known either respecting these 
orbs themselves or their primaries. It seems clear that 
Sir "William Herschel was mistaken as respects four of 



* About 93° according to the best estimates of the dimensions of the 
rings and the distance of the satellite. 



202 OTHER WORLDS THAN OURS. 

the satellites of Uranus he supposed he had detected. 
Uranus has but four known satellites and Neptune only 
one. Possibly other Uranian satellites may one day be 
discovered, and Neptune also may possibly have several 
satellites circling around him. But only the five bodies 
above-mentioned are at present known. 



METEORS AND OOMETS. 20o 



CHAPTEK IX. 

METEORS AND COMETS I THEIR OFFICE IN THE SOLAR 
SYSTEM. 

There are few more interesting chapters in the history 
of astronomy than that which deals with the gradual in- 
troduction of meteors into an important position in the 
economy of the solar system. Regarded for a long time 
as simply atmospheric phenomena (though many ancient 
philosophers held another opinion), it has only been 
after a long and persistent series of researches that they 
have come at length to be regarded in their true light. 
But though the history of those researches is not only 
full of interest, but highly instructive and encouraging, 
this is not the place for entering at length into its de- 
tails. I must present facts and conclusions, rather than 
the narrative of observations or calculations by which 
those facts and conclusions have been established. Nay, 
it would seem at first sight as though even the nature of 
meteors could have very little to do with the subject of 
this treatise, since we cannot suppose these small bodies 
to be inhabited worlds. It will be found, however, that, 
though this is certainly true, there are reasons for believ- 



204 OTHER WORLDS THAU OUBS. 

ing tliat meteors are associated in a very intimate manner 
with the general relations of the family of worlds forming 
the solar system 

Under the head " Meteors " I include all those objects 
which reach the earth's atmosphere from without, 
whether they actually make their way to her surface un- 
broken, like the aerolites ; or explode into small frag- 
ments, as bolides and fire-balls have been observed to 
do ; or are apparently consumed in traversing the upper 
regions of the air, as happens with shooting or falling 
stars. All these objects, we now know, represent in real- 
ity bodies of greater or less size, which, before their en- 
coanter with the earth, were travelling around the sun in 
orbits of greater or less eccentricity. The larger masses, 
though they must be very numerous (or our earth would 
not once in many ages encounter any of them), are yet 
relatively few in number as compared with fire-balls, and 
still more so in comparison with shooting stars. It has 
been calculated, indeed, that these last are so numerous 
that the earth, in passing through a region of space equal 
to her own dimensions, must encounter no less than thir- 
teen thousand of them ; while of yet smaller bodies, 
whose passage through our air would only be recogniza- 
ble by telescopic aid, she is supposed to encounter as 
many as forty thousand within a similar space. Without 
laying great stress on these calculations, we may yet feel 
quite sure that the earth must encounter enormous num- 
bers of these bodies, from the mere fact that, though at 



METEORS AND COMETS. 205 

any fixed station but a minute slico (so to speak) of the 
earths atmosphere is within view, and ovon but a por- 
tion only of that slice visible to a single observer, six or 
seven falling- stars on the average may bo soon during 
each hour of the night. 

It will bo soon, then, that a problem of the utmost im- 
portance was involved in the question whether these bod- 
ies came from the interplanetary spaces, or from the 
region oi space over which tho earth's own attractive 
energies prevail. Now that wo know tho former view to 
be tho true one, we recognize tho fact that, though each 
meteor may be individually insignificant, tho meteors of 
tho solar system, looked on as a single family, form a 
highly interesting and important portion of the sun's 
domain. 

But now a yet more significant relation has to be con- 
sidered. Regarding meteors as planetary bodies, they 
might yet bo relatively unimportant, if wo had any rea- 
son to believe that they form a sort of zone or bolt near 
the earth's orbit, resembling in a sense the asteroidal 
zone, only composed of Ear smaller constituent bodies. 
We could not thai infer from the number of meteors en- 
countered in a given time by tho earth, the largeness of 
tho total number of these bodies ; for it might well be 
that this zone had no counterpart, either in the outer 
part of the planetary system or within tho orbit of the 
earth. What has actually boon discovered, however, re- 
specting the paths along which the meteoric bodies have 



206 OTHER WORLDS THAN OURS. 

reached the earth, immensely enhances the importance 
of these objects. 

It has been proved, on evidence perfectly incontesta- 
ble, that two well-marked meteoric systems travel in 
orbits of enormous eccentricity. The August meteors 
travel on a path so eccentric that in the neighborhood 
of the earth's orbit it may be regarded as almost para- 
bolic in figure. That it is not absolutely parabolic is 
shown, of course, by the fact that a period has been as- 
signed to the revolution of the members of the zone. No 
observations have indeed been made by which astrono- 
mers could determine the orbit of these meteors, since 
for this purpose an exact determination of the velocity 
with which they enter the earth's atmosphere would be 
requisite, while the observations actually made to de- 
termine their velocity are confessedly inexact. But an 
association, altogether too close to be regarded as acci- 
dental, has been discovered between their orbit and that 
of a bright comet which appeared in 1862, and this, 
combined with what has since been established respect- 
ing the relations between comets and meteors, enables 
astronomers to adopt quite confidently the orbit of the 
comet as that of the meteoric system. Now a period of 
145 years implies, according to Kepler's law, an orbit 
having a mean distance nearly equal to that of Neptune. 
And since the orbit is so eccentric as to bring these 
bodies close to the earth when they are near perihelion, 
it follows that their aphelion distance must exceed their 



METEORS AND COMETS. 207 

mean distance in the same degree. Hence the aphelion 
point of the August meteors must lie nearly twice as far 
away from us as the orbit of Neptune. 

The November meteors have been shown in like 
manner to travel in a period of 33J years around the 
sun, the aphelion of their orbit lying far beyond the 
path of Uranus. 

So far, then, as we can judge from the only two 
meteoric systems whose orbits can be said to have been 
satisfactorily determined (though there are many other 
systems which have been associated with known comets), 
we are led to the conclusion that the meteoric orbits 
are for the most part eccentric. We know, further, that 
they are inclined in all directions to the plane in which 
the earth travels, because we see that their constituent 
bodies fall upon the earth in directions which show no 
tendency to near coincidence with the ecliptic. 

These two circumstances are full of meaning. If the 
meteors travelled in nearly circular orbits at a mean dis- 
tance nearly equal to the earth's mean distance from the 
sun, then the earth would be certain to encounter mete- 
ors in the course of her orbital motion round the sun. 
Again, if the meteors travelled in eccentric orbits, whose 
perihelia lay within the earth's orbit, and if these orbits 
all lay in or near the plane of the earth's path, the earth 
could not fail to encounter meteors as she travelled round 
the sun. But under the actual circumstances — the mean 
distances of the meteoric orbits being in no way associated 



208 OTHER WORLDS THAN OURS. 

with the earth's mean distance, and the inclination of 
these orbits to the ecliptic not being in any way limited 
— the two questions are at once suggested, (1) "What 
is the a priori chance that the earth would encounter 
the members of any meteoric system taken at random ? 
and, (2) If this chance be small, what is the conclusion to 
be drawn from the fact that the earth encounters meteors 
belonging to many systems ? — the number already recog- 
nized being nearly sixty. Assigning elements at random 
to a meteor system, we see that, unless the resulting orbit 
actually coincides with the plane of the ecliptic (a relation 
which would not happen in a million trials), the orbit 
will intersect that plane in two points, lying on a straight 
line through the sun. And for the earth to encounter 
members of the meteoric system, it is requisite that one 
or other of these two points shall lie close to the earth's 
orbit. But these points may have any position whatever 
in the plane of the ecliptic, and the chance that one of 
them has the requisite position may be regarded as in- 
definitely small. It follows, then, that the a priori chance 
of the earth's encountering the members of a meteoric 
system is indefinitely small ; and hence we conclude that 
the number of meteoric systems of which she passes 
wholly clear is indefinitely great, in comparison with the 
number whose members she encounters. But she actually 
encounters meteors belonging to more than four hundred 
systems. Hence the total number of meteoric systems 
belonging to the planetary scheme must be an indefinitely 



METEORS AND COMETS. 209 

large number of hundreds — or in other words, it must be 
enormously beyond our powers of conception. 

This being so, it behooves us to inquire, first of all, what 
extent we must assign to indiyidual meteoric systems, and 
how densely we may suppose meteoric masses to be 
strewn along each system ; and secondly, what may be the 
nature, quality and substance of these meteoric masses. 
For we begin to see that we are in the presence of relations 
which may — or I should rather say, which must — affect 
most importantly the economy of the solar system. 

Now we have seen something already of the longitudinal 
extent of meteoric systems, since that extent corresponds 
to the circumference of meteoric orbits, and we have seen 
that these orbits have enormous dimensions. We may 
indeed suppose that in some cases the whole extent of an 
orbit is not occupied by meteoric masses at any one 
instant : but even when, as in the case of the November 
meteors, the annual displays wax and wane in splendor, 
there is no absolute cessation in the occurrence of star-falls 
on the date corresponding to such a system. And taking 
full account even of the marked diminution which actually 
occurs, we are yet compelled to assign an enormous longi- 
tudinal extent to that portion of the system which has 
been poetically termed "the gem of the meteor-ring." 
For example, in the November meteor system, this portion 
of the ring cannot be less than one thousand million miles 
in length. As to the width of a meteor system — that is, 

its extent in a direction measured in the plane of its orbit 
14 ___ 



210 OTHER WORLDS THAN OURS. 

— we have no satisfactory information, because a meteoi 
system may extend enormously on either side of the point 
through which the earth's orbit intersects it, and yet no 
trace of that extension be recognized by observers on the 
earth. Still we may conclude that this dimension lies in 
extent somewhere between the longitudinal extension of 
the system and the depth of the meteor zone — that is, 
the length of a line taken through it, square to the plane 
in which it lies. Now of this last dimension we can form 
a tolerably accurate estimate in many instances. "We 
know that so long as meteors belonging to any system are 
flashing into view, our earth is still plunging through the 
system ; and if we know the position of the system, we 
can determine its depth in this way, just as we could de- 
termine the breadth of a range of hills if we noticed the 
time occupied by a train, travelling with known velocity, 
in passing through a tunnel which traversed the range of 
hills in a known direction. Judged in this way, the depth 
of the November meteor zone would seem to be one hun- 
dred thousand miles in the part traversed by the earth hi 

1866, about sixty thousand miles in the part traversed in 

1867, and considerably greater (though the zone was more 
sparsely strewn with meteors) where the earth crossed 
the system in 1868, 1869, and 1870. 

. Now as regards the density with which meteors are 
strewn in any known system, I must remark on a mistake 
which has been sometimes made. It has not been thought 
necessary to consider the velocity with which the meteors 



METEORS AND COMETS. 211 

themselves travel, as well as tlie earth's velocity, in order 
to determine from the average interval of time separating 
the appearance of successive meteors the average distance 
separating neighboring meteors from each other. This, 
however, is an erroneous mode of dealing with the prob- 
lem. We must consider the meteoric velocity, since the 
meteoric motions manifestly tend to affect the total num- 
ber of encounters.* Let us apply this consideration to 
enable us to form a rough estimate of the number of bodies 
in the richer part of the November meteor system. We 
may fairly assume that, taking the average of the four 
displays of the years 1866-69, the earth encountered 
more than one meteor per minute as she swept onward 
through the system ; or, coveniently for our purpose, 
that an average distance of one thousand miles separates 
meteor from meteor throughout the " gem of the ring." 
Now the length of the great cluster is at least 1,000,- 
000,000 miles, its thickness may be fairly assumed as 
averaging 100,000 miles, and its width can hardly be less 
than ten times its thickness, since the forces acting on 
the system tend much more largely to affect its width than 
its thickness. Thus, with the assumed average of distance 



* Obviously the total number of meteors encountered during the 
earth's passage through a meteor stream will be the number contained 
in a cylindrical space having a cross-section equal to the earth's, and 
traversing the meteor stream from side to side. The motion of tbe me- 
teors will affect the particular set of meteors actually found within this 
space as the earth traverses it, and will also afreet their number, assum- 
ing a general uniformity of meteoric distribution. 



213 OTHER WORLDS THAN OURS. 

(1,000 miles), we find that the cluster cannot contain less 
than (1,000,000 x 100 x 1,000) or one hundred thousand 
million meteors ! 

Professor Alexander Herschel, from observati ms of the 
amount of light given out by these bodies, and a calcula- 
tion founded on the velocity with which they penetrate 
our atmosphere, has come to the conclusion, that they 
must, for the most part, be very small, rarely perhaps, 
exceeding a few ounces in weight. "We shall certainly 
not exaggerate their weight if we assign the one hun- 
dredth part of an ounce to each. We thus obtain for the 
tveight of the whole cluster one thousand millions of 
ounces, or about twenty-eight thousand tons. The actual 
weight of the November meteor system cannot, however, 
but enormously exceed this amount; and therefore we 
recognize how erroneous that opinion is which an emi- 
nent astronomer has expressed, who asserted that the 
united weight of all the bodies other than planets in the 
solar system must be estimated rather by pounds than by 
tons. We have certainly no reason for thinking that the 
November system, though one of the most important en- 
countered by the earth, is exceptionally important in the 
solar system. On the contrary, we have every reason 
which the laws of probability can afford us for believing 
that there must be millions of systems equally or more 
extensive. And further, the fall of enormous masses, 
many tons sometimes in weight, upon the earth, would 
point to the conclusion that the members of the Novem- 



METEORS AND COMETS. 213 

ber system are exceptionally insignificant as regards their 
individual dimensions. So that we seem forced to the 
conclusion that the aggregate weight of the various mete- 
oric systems circulating around the sun must be esti- 
mated by billions of tons rather than by any of our ordi- 
nary units. 

I have already referred to the relation which has been 
detected between comets and meteor systems. Perplex- 
ing as the relation appears, it has been established on 
evidence which cannot reasonably be disputed. It car- 
ries with it results of extreme interest and importance. 

I do not propose here to enter into any consideration 
of those enormously difficult questions which are sug- 
gested by the study of cometic phenomena. That they 
will before very long receive their solution I confidently 
believe ; but in the present state of our knowledge it 
would indeed be hazardous to speculate as to what that 
solution may be. I may remark, in passing, that while I 
recognize in recently promulgated theories on the sub- 
ject the indication of a highly suggestive and promising 
line of research, I cannot but feel that cometic phenomena 
are far too complicated to be directly accounted for in any 
of the ways pointed out of late by physicists. Some of 
the more obvious, and, I may add, the more generally 
known phenomena, do indeed appear to receive a solution 
when examined under the light of recent researches, but 
numbers of others not only remain unaccounted for, but 
stand apparently altogether opposed to suggested theories. 



214 OTHER WORLDS THAN OURS. 

For my present purpose, however, the facts to be prin- 
cipally noticed are in a sense independent of any views 
which may be formed respecting the nature of comets. 
We know that the dimensions of these objects are in many 
cases enormous. We know, further, that there must be 
many thousands of comets remaining undiscovered, for 
each that our astronomers have detected. And, lastly, 
we are led to recognize the observed association between 
certain meteor systems and certain comets as indicative 
of a general law by which, in some way as yet unex- 
plained, comets and meteors are associated together. 
Thus, independently of the considerations already ad- 
duced, we are led to the conclusion that meteor systems 
must be very numerous; while from the fact that a 
meteor system so important as the November stream is 
associated with a comet so insignficant as Tempel's, we 
conclude that those magnificent comets which have 
blazed in our skies — a source at once of wonder and per- 
plexity to the astronomer — must be associated with sys- 
tems of bodies incalculably more important than the 
meteor system which has so often filled the heavens with 
falling stars. 

Combining all these results, we seem fairly led to the 
conclusion that purposes of importance in the economy 
of the solar system are probably subserved by these un- 
counted thousands of meteoric streams. If, indeed, we 
could suppose that the planets steered clear of them, and 
that the bodies composing them simply circulated un- 



METEORS AND COMETS. 215 

ceasingly in their orbits, we might form another opinion. 
But we know that meteors are continually falling upon 
the atmosphere of our own earth, either there to be dissi- 
pated into finest dust, or to pass onward, with or without 
explosion, to the actual surface of the earth ; and we 
cannot doubt that in a similar way countless thousands of 
meteors are falling, not only upon all the primary mem- 
bers of the solar system, but upon asteroids and satellites 
— nay, are even streaming in among the minute bodies 
composing the rings of Saturn. These encounters cannot 
be wholly without result, and it is quite conceivable that 
most injurious consequences might ensue to the inhabi- 
tants of all the worlds in the solar system if the contin- 
ual supply of meteoric matter were importantly dimin- 
ished. 

Now, if meteoric masses fall continually upon the plan- 
ets, such masses must fall in numbers inconceivably 
greater upon the sun ; and it is here, unless I mistake, 
that the great purpose of the meteoric systems becomes 
apparent. 

Let us clearly recognize, however, why and how the 
sun must be assaulted by a continual inrush of meteoric 
bodies. We have seen how enormous must be the num- 
ber of these bodies; we know how swiftly they travel, 
and on what eccentric orbits ; but we must go further be- 
fore we can prove that they fall upon the sun. For ex- 
ample, the November meteors are enormous in number, 
and travel with enormous velocity in a very eccentric or- 



216 OTHER WORLDS TBAN 0U£$. 

bit, but they do not approach the sun within a distance 
of nearly 90,000,000 miles. Nor, indeed, can any known 
meteoric system pour a steady hail of meteors, so to 
speak, upon the sun ; for he is the ruling centre of every 
meteoric system, and therefore under ordinary circum- 
stances the meteoric orbits must pass around him, and 
not in such directions as to intersect his substance. 

But it is to be remembered that meteors must be infi- 
nitely more crowded in the neighborhood of the sun than 
at a distance from him. An indefinitely large number of 
meteoric orbits must absolutely intersect in the immedi- 
ate neighborhood of the sun ; and collisions must be con- 
tinually taking place as countless thousands of meteoric 
flights rush toward and past and then away from their 
perihelia. "Where these perihelia lie close to the sun the 
Telocity with which the meteors travel must exceed two 
hundred miles per second, and therefore the collision 
even of two minute meteors must result in the generation 
of an enormous amount of light and heat. But that is 
not alL Among the collisions thus continually taking 
place in the sun's neighborhood there must be a consid- 
erable proportion in which the two bodies are brought 
momentarily almost to rest by the shock. In such 
cases the combined mass of the two meteors would fall 
directly upon the sun, a fresh supply of light and heat 
being generated as they were brought again to rest upon 
his surface. 

Whether in the continual collisions of meteors among 



METEORS AJTD COMETS. 21? 

themselves, and in their precipitation npon the sun's sur- 
.. we hai ait explanation of the seemii 

m of light and heat from the sun, I 
lid not care positively to assert. Sir W. Thorn] 

who was one of the first to adopt this view, has : 
abandoned it ; though it is worthy of remark t 
strongest evidence in its favor has been obtained since he 
withdrew his support from it. or at least admitted that 
the downfall of meteors on the sun's surface is not tzfrni 
sufficient to account for the solar light and heat. But so 
far as I can judge, there is no flaw in the evidence I h 
adduced from the laws of probability applied to recent 
discoveries ; and that we are bound to accept as a legiti- 
mate conclusion from that evidence the theory that at 
least a proportion of the sun's heat is supplied from the 
meteoric streams which circulate in countless millions 
around him. It can no longer be believed, however, 
without adopting unreasonable assumptions, that the 
whole of that enormous supply of light and heat which 
the sun emits on every side is derived from the meteoric 
vma belonging to the solar system or drawn in from 
surrounding space, as the sun, attended by his family of 
planets, sweeps onward amid the stellar groups. 

If this view were correct, then the meteor systems 
would constitute indeed a most important part of the sun's 
domain. They might be said almost to share with the 
sun a title to be regarded as the source of all the forms of 
force which exist throughout the solar system. If in the 



218 OTHER WORLDS THAN OURS. 

energies of living creatures on earth, in the forces derived 
from the fuel that propels our engines, or in the power of 
winds and storms, we trace the action of the ruling centre 
of the solar system, we might trace back the chain of 
causation yet one link further, and see in the sun's emis- 
sion of light and heat the result of forces inherent in the 
meteoric systems which circle around him. 

But we must not forget one most important considera- 
tion, which would make the sun (as might be anticipated) 
again the chief source of all the forms of force existing 
within his system. The motions of the meteoric masses 
are almost wholly due to the sun's attraction ; and there- 
fore, in so far as those motions are to be regarded as a 
means of renewing the solar heat, we must regard the 
sun's attractive energy as the source whence his heat and 
all the other forms of force which he exerts are in reality 
derived. 

Yet one step further. The sun's attractive energies 
might be increased a thousand-fold, and yet not avail to 
supply the various forms of force which are required by 
his dependent worlds, were there no external material on 
which those energies could act in such sort as to lead to 
the continual inrush of matter upon the solar surface. 
Nor would it suffice if such materials, even in enormous 
quantities, existed close to the sun. It is the distance 
from which that material is dragged toward the sun which 
gives that orb the power of imparting those tremendous 
velocities to which the collisions of the meteoric bodies 



METEORS AND COMETS, 219 

owe their real effectiveness. We thus find in distance, in 
the simple element of scale, the true source of the various 
forms of force which are continually exerted throughout 
the solar system. The sun surrounded by millions on 
millions of meteoric masses close at hand would be power- 
less ; but placed as ruler over a space far wider than the 
sphere circled by Neptune's orbit, amid which space 
those countless millions of meteors are distributed, he 
becomes forthwith the centre of a thousand forms of en- 
ergy, gathered by him continually from the systems of 
meteors circling around him, and distributed by him 
abundantly and without ceasing to his dependent worlds.* 
It will not fail to be noticed by the thoughtful reader 
that, adopting this view of the relation in which meteoric 
and cometic systems stand with respect to the sun, it seems 
necessary that we should regard those planets which I 
have endeavored to raise to the dignity of secondary 
suns, as subordinate centres of attraction, around which 
countless thousands of meteoric systems may be supposed 



* Just as this work (the first edition) was about to be placed in the 
printer's hands I received from Professor Kirkwood, of America, one 
of his valuable contributions to the history of the solar system. In it 
he points to the evidence we have that the sun, as he speeds onward 
through space, passes through regions in which cometic and meteoric 
materials are now richly, now sparsely strewn, and gathers in accord- 
ingly new stores of force of greater or less amount. The bearing of the 
views of this acute and soundly reasoning astronomer (the Kepler of 
our day), not only on the theories dealt with in the above chapter, 
but on those considered in the chapters which follow, will be seen at 
once. 



220 OTHER WORLDS THAN OURS. 

to circle. Have we any evidence pointing to such a con« 
elusion ? 

Now there can be no doubt that if Jupiter, the nearest 
of these secondary suns, did so act upon a passing comet 
as to compel that body to circle in future around Mm, 
instead of pursuing its course around the sun, we could 
not in any way become cognizant of the event unless the 
comet were an exceptionally large one. I conceive, how- 
ever, that such an event, though undoubtedly possible,* 
must be so uncommon that the number of cometic sys- 
tems thus forced to own Jupiter as their centre of attrac- 
tion must be relatively few. But in another way the 
planet does exhibit his power as a comet-ruler, making 
comets recognize him as a sort of subordinate master, the 
sun being their primary ruler. When comets coming from 



* It is necessarily possible in the case of any planet, but must in 
many cases be highly improbable. For example, astronomers some- 
times assert that meteoric masses passing near the earth might become 
satellites of hers ; but in reality this is a very unlikely event, because 
the maximum velocity which a body travelling under the earth's influ- 
ence can have (that is, the velocity acquired by a body travelling from 
infinity to a perigee close to the earth) is less than the velocity with 
which a body circling on any orbit round the sun would move when at 
the earth's distance from him, unless its orbit were very eccentric and 
the aphelion close by the earth's orbit. Bodies travelling from outer 
space toward the sun cannot by any possibility become satellites of the 
earth, because they would always have a velocity greater than that 
which her attraction can master. Even in the rare event of their 
grazing her atmosphere, and so losing a large share of their velocity, 
they could not become permanent satellites of hers, because, returning 
to the scene of encounter, they would lose yet a larger share of their 
velocity, and so must be brought, and that soOn, to her surface. 



METEORS AND COMETS. 221 

outer space pass near enough to Jupiter, he sways them 
so markedly from the orbit they are pursuing that the 
scene of encounter becomes the aphelion of their orbit, 
or nearly so. Thence they pass on their new orbit to 
their perihelion, returning again presently to the scene 
of their encounter with Jupiter, and so revolving in an 
orbit having its aphelion close by the orbit of Jupiter, 
until haply the giant is again near the scene of encounter 
at the moment when the comet comes back to it. In this 
case a fresh struggle takes place, the overmastering at- 
traction of the planet necessarily prevailing, and the com- 
et being often dismissed on a new orbit, whose perihelion, 
instead of its aphelion, lies close by the orbit of Jupiter. 

Now we know that such events as these must be of fre- 
quent occurrence as Jupiter sweeps swiftly round on his 
orbit. For we recognize several comets which have evi- 
dently been compelled by Jupiter to take up such orbits 
as I have spoken of — a family of comets, in fact, including 
Encke's, Faye's, and Brorsen's, Winnecke's short-period 
comet, and several others. "We judge further, from the 
laws of probability, that for each discovered comet of this 
family there must be thousands which have escaped detec- 
tion. So that around the orbit of Jupiter (if not around 
Jupiter himself) there cling the aphelia of myriads of 
cometic orbits whose perihelia lie at all conceivable dis- 
tances from the sun less than the distance of Jupiter. 

Saturn also has his family of comets ; so also have 
Uranus and Neptune. The comat associated with the 



223 OTHER WORLDS THAN OURS. 

November meteors belongs indeed to the Uranian comet- 
family, and the epoch (126 A.D.) has even been pointed 
out when this comet may have fallen under the dominion 
(subject always to the sun's superior control) of that dis- 
tant planet. 

And here I may refer to a view which I have long 
entertained respecting the purposes which meteoric and 
cometic systems have fulfilled in the past history of the 
solar system.* We know that the materials composing 
meteors, and we conclude, therefore, that those composing 
comets do not differ from those which constitute the earth 
and sun, and presumably the planets also. Therefore 
under the continual rain of meteoric matter it may be said 
that the earth, sun, and planets are growing. Now the 
idea obviously suggests itself that the whole growth of the 
solar system from its primal condition to its present state 
may have been due to processes resembling those which 
we now see taking place within its bounds. It is of course 
obvious that if this be the case, the number of meteoric 
and cometic systems must have been enormously greater 
originally than it is at present. Countless millions of 
meteoric systems, travelling in orbits of every degree of 

* Since the present chapter was written, I find that the hypothesis 
here put forward has in a general way been touched on by more than 
one astronomer and physicist. I believe, however, that here, for the 
first time, it has been associated with the chief features of the solar 
system. It was suggested in note B (Appendix) to my treatise on Saturn. 
But as a matter of fact, when that note was written, as also when those 
passages were published in which the same hypothesis is dealt with by 
other authors, decisive evidence in favor of the theory was wanting. 



METEORS AND COMETS. 22& 

eccentricity and inclination, travelling also in all conceiv- 
able directions around the centre of gravity of the whole, 
would go to the making up of each individual planet. A 
marked tendency to aggregate around one definite plane, 
and to move in directions which, referred to that plane, 
corresponded to the present direction of planetary motion, 
would suffice to account for the present state of things. 
The effect of multiplied collisions would necessarily be to 
eliminate orbits of exaggerated eccentricity, and to form 
systems travelling nearly in the mean plane of the aggre- 
gate motions, and with a direct motion. Further, where 
collisions were most numerous, there would be found not 
only the most circular resulting orbits, not only the great- 
est approach to exact coincidence of such orbits with the 
mean plane of the whole system, but the bodies formed 
out of the resulting systems would there exhibit rotations 
coinciding most nearly with the mean plane of the entire 
system.* 

It seems to me that not only has this general view of 
the mode in which our system has reached its present state 
a greater support from what is now actually going on than 
the nebular hypothesis of Laplace, but that it serves to 
account in a far more satisfactory manner for the principal 



* This conclusion depends on a well-known law of probability. It 
may be thus illustrated: If we have in a bag a million white and a 
million black balls, and takeout at random a number of balls, then the 
larger that number, the more nearly (in all probability) will the number 
of black and white balls included in it approach to a ratio of equality. 



224 OTHER WORLDS THAN OURS. 

peculiarities of the solar system. I might indeed go 
further and say that where these peculiarities seem to 
oppose themselves to Laplace's theory, they give support 
to that which I have put forward.* 

For example, what is there in the nebular hypothesis 
which affords even a general explanation of the strange 
varieties of size observed in the planetary system ? How 
can that hypothesis be reconciled with the remarkable 
variations of inclination observed among the planets, or 
with the retrograde and almost perpendicular motion of 
the satellites of Uranus ? Nor, again, is the hypothesis 
consistent with the observed peculiarities of motion of 
those meteoric systems which we must now regard a& 
regular members of the solar system. 

Now, according to the hypothesis I have put forward 
above, a general explanation of all these matters is at 
once suggested. Let us consider : 

In the neighborhood of the great central aggregation 
which would undoubtedly result from the motions of 
such meteoric systems as I have considered, all the mo- 
tions would be very rapid. They would, in fact, resemble 
the motions now actually observed in the sun's neighbor- 



* It is scarcely necessary to remark that as regards at least the larger 
members of the solar system — including the four primary planets with- 
in the zone of asteroids— the nebulous condition inferred by Laplace 
would necessarily result from the processes above suggested ; so that, in 
a sense, the above account may be supposed to describe a state of things 
antecedent to the nebulous condition of the planets and sun, as con- 
ceived by Laplace. See also note B to my treatise on Saturn. 



METEORS AND COMETS. 225 

hood. Here, therefore, subordinate aggregations would 
form with difficulty, since they would have small power 
of overruling meteoric systems rushing with so great a 
velocity past them. In the sun's immediate neighbor- 
hood, then, we should expect to find relatively small 
planets; and we do accordingly find that Mercury, near- 
est to him, is the smallest of the planets, Yenus larger, 
and the earth (yet further away) not only larger than 
VenuSj but adorned with an attendant satellite. 

Now, at a much greater distance from the sun the 
meteoric motions would be so much less than here, sup- 
posing only a suitable mean density of aggregation, it 
would be possible for much larger subordinate centres of 
aggregation to form. These centres would increase in 
importance as they swept round the central aggregation, 
continually gathering fresh recruits. Indeed, though, as 
now, they would not be able to prevent the major part of 
the materials rushing from outer space toward the sun 
from aggregating round him, they would still gather in no 
inconsiderable portion of those materials. Where the 
largest portion would be gathered would depend on the 
way in which (taking a general view of the system) the 
quantity of material increased toward the neighborhood 
of the centre. For clearly, while distance from the sun' 
would increase the facility with which materials would be 
gathered in — since the sun's influence would diminish 
with distance it would also affect the quantity of material 

available — since, from a very early period, the system 
15 



226 OTHER WORLDS THAN OURS. 

must have begun to show an appearance resembling that 
now presented by the zodiacal light — that is, a general in- 
crease of density toward the centre. 

Assuming that the region of maximum aggregation was 
that where the influence of the ruling centre first became 
so far diminished with distance as to render the for- 
mation of a great subordinate aggregation possible, we 
should have the innermost of the outer series of planets 
also the most bulky ; and next within the orbit of that 
giant planet we should find a relatively barren space, 
cleared of material not only by the sun's still powerful 
influence, but also by the influence of this first important 
subordinate aggregation. The initial assumption is, in 
itself, at least not improbable, and having once admitted 
it, we find an explanation of the giant mass of Jupiter, of 
the comparative poverty of material just within the orbit 
of Jupiter, and hence of the condition of the asteroidal 
zone, and of the smallness of the planet Mars next within 
that zone — though this planet far outweighs (according to 
Leverrier's estimate) the united mass of all the asteroids. 
Beyond the orbit of Jupiter, we should expect (after pass- 
ing an enormously wide space, bare of worlds) to find 
still a great abundance of material, and an even greater 
facility in the aggregation of that material. Thus the ex- 
istence of the planet Saturn, next in importance to Jupi- 
ter, and surpassing him in the complexity of his attend- 
ant system, is accounted for ; yet further away, we look for 
and find still an abundance of material, and that materia* 



METEORS AND COMETS. 227 

somewhat more uniformly strewn, while the sun's small 
influence is indicated by the existence of satellites, of 
which doubtless many more will one day be discovered by 
astronomers. 

As to the rotations of the various members of the solar 
system we find some account, necessarily not exact, given 
by this theory. I have mentioned above the results to be 
looked for; those observed are closely accordant with 
that view. Thus the sun, the largest member of the sys- 
tem, and specially pre-eminent within its inner division, 
has its equator inclined but about 7° to the mean plane 
of the system. Mars, the least member of this system, 
has an inclination of no less than 28°; the larger earth an 
inclination of but 23°. The inclination of Venus and 
Mercury are undetermined ; they may be expected to be 
large, not merely on account of the smallness of these 
bodies, but on account of their proximity to the sun. Of 
the outer division of the system, Jupiter, the largest, has 
an inclination of little more than 3°; Saturn has a very 
considerable inclination (more than 26°) ; Uranus has an 
inclination which may be described as actually greate* 
than 90°, since he rotates backward with his equator in- 
clined 76° to the ecliptic. And lastly, if the observations 
hitherto made on Neptune's satellites are to be trusted, 
this planet probably rotates in a retrograde manner, his 
equator being inclined some 26° to the horizon, so that, 
to render the comparison between his rotation and that 
of the other members of the solar system complete, he 



228 OTHER WORLDS THAN OURS. 

may be said to rotate in a direct manner with his equator 
inclined some 154° to the ecliptic. 

The great inclination and eccentricity of many of the 
asteroidal orbits is also accounted for more satisfactorily 
by this theory than by the nebular hypothesis. There is 
perhaps no absolute incorrectness in the assertion that 
the smallness of the asteroids explains (on the ordinary 
view of their origin) the relatively irregular nature of 
their motions. Their minuteness doubtless brings them 
(when long intervals of time are considered) more under 
the disturbing influence of Jupiter than a single massive 
planet at the same distance from the sun would be.* 



* The most eminent astronomer of our day indicated in a private 
communication an objection to this sentence (originally written without 
the parenthetical passage), founded on the fact that the disturbance by 
Jupiter of a single planet as large as the earth (or even Neptune) trav- 
elling on the orbit of one of the asteroids, would be precisely the same 
as the disturbance of the asteroid, or even of a much minuter body — as 
a meteor or a peppercorn. This is just ; but the contrary was not 
meant to be implied by the above sentence as it originally stood. It 
was to the influence of Jupiter in long cyclic periods, during which the 
reflex actions due to the changes in Jupiter's own orbit through the ac- 
tion of the perturbed body came into play, that I referred. In the case 
of two planets of nearly equal mass — or of masses comparable in magni- 
tude — there is an interchange of eccentricities and inclinations, and 
these can never become very large for either planet. It is different, 
however, when one of the bodies is exceedingly minute, for then the 
orbit of the larger changes so slowly that perturbing effects are renewed 
again and again, during a very long cycle, so that before the reverse 
processes begin to act a very considerable eccentricity or a very consid- 
erable inclination may be given to the smaller body. That this is so ig 
shown by the much wider range within which the eccentricities and in- 
clinations of the smaller planets of the solar system are known to oscil- 
late in long intervals of time. 



METEORS AND COMETS. 229 

But the attraction of Jupiter can scarcely have been suf- 
ficient to cause the asteriods to depart so widely as they 
do from the ecliptic, since his path lies quite close 
to the ecliptic, and even nearer to the mean plane of 
the solar system. Bodies formed as the asteroids are 
supposed to have been, according to the hypothesis I 
have suggested, would necessarily exhibit a much greater 
variety of motion than would be recognized in the case of 
the larger planets. 

Another point in which, as I conceive, my hypothesis 
is more satisfactory than the nebular one consists in the 
fact that it suggests an explanation of the peculiarities 
observed in the planetary periods. Professor Kirkwood's 
researches into the various relations of commensurability 
presented among the periods of planets and satellites, 
and the known effects of commensurability in encourag- 
ing the accumulation of planetary perturbations, will at 
once suggest to the mathematical reader the way in which 
a system forming in such a manner as I have imagined 
might be expected to exhibit the presence of law as 
regards distances and periods. There is nothing in the 
nebular hypothesis which encourages the belief that a 
system framed as Laplace conceived the solar system 
to be, would exhibit any such laws as are found vithin 
the planetary scheme. 

The hypothesis I have put forward also gets rid of 
what has always seemed to me the great difficulty of 
the nebular hypothesis. According to the views of La- 



230 OTHER WORLDS THAN OURS. 

place, Neptune must have been formed millions of ages 
before Uranus, Uranus as long before Saturn, Saturn as 
long before Jupiter, and so on. Now we know that the 
appearance of those primary members of the solar system 
which we are best able to stud}?- does not indicate any 
such enormous disproportion in the ages of the planets, 
even if it does not indicate that the planets were formed 
nearly at the same era. According to my hypothesis, the 
various processes of aggregation would go on simultane- 
ously (just as the influences which Jupiter now exerts 
on comets act simultaneously with the more powerful in- 
fluences exerted by the sun) ; and though the various 
orbs formed by those processes would not necessarily be 
completed simultaneously, there would be no such enor- 
mous disproportion in their age as is necessary according 
to the theory of Laplace. 

Yet another strong point in favor of this hypothesis 
resides in the circumstance that we now have every reason 
to believe, that all the planets are constituted of the 
same elements. "When it was thought that Jupiter might 
be a watery globe, for instance, there was some evi- 
dence in favor of Laplace's theory. But we now know 
that Jupiter is not constituted differently, in all proba- 
bility, from the earth and sun, as according to Laplace's 
theory he must have been. Since, then, we know that 
meteors contain the same elements which exist in the 
constitution of sun and planets, we have here a very 
strong argument in favor of the view that they have 



METEORS AND COMETS. 231 

played the important part I have assigned to them in the 
formation of the solar system. 

But after all, the strongest evidence in favor of the 
hypothesis I have suggested consists in the fact that the 
processes by means of which I conceive the solar system 
to have been formed are undoubtedly going on before 
our eyes. There may be little," indeed, in the downfall of 
meteoric showers to suggest the idea of world-formation 
or sun-formation; little in the present aspect of the 
zodiacal light or of the solar corona to present to the 
mind's eye a picture of that vaster agglomeration of me- 
teoric and cometic systems, all speeding with inconceiva- 
ble velocities on their interlacing orbits, which I imagine 
to have been the embryon of the solar scheme. But sun 
and planets are growing, however slowly, as the meteoric 
hail falls continuously upon them ; the zodiacal light and 
the solar corona are doubtless due to the existence of me- 
teoric systems, resembling (however relatively insignifi- 
cant) those which I have pictured as the materials of the 
planetary scheme. In the Saturnian rings, also, which 
have been proved by the researches of Maxwell and others 
to consist of multitudes of discrete bodies, we have evidence 
of the same sort in the case of a subordinate centre of ag- 
gregation. So that we have a form of evidence, which was 
wanting in the case of the nebular hypothesis, in favor of 
this other hypothesis, by which, as in Laplace's, the pres- 
ent state of the solar system is regarded as the result of 
a process of development, and not of special creative fiats. 



£32 OTHER WORLDS THAN OVS& 



CHAPTEE X. 

OTHER SUNS THAN OURS. 

We are now to venture into regions where we shall no 
longer have clear lights to guide us. Tremendous as are 
the dimensions of the solar system, the widest sweep of 
the planetary orbits sinks into insignificance compared 
with the distances which separate from us even the near- 
est of the fixed stars. From beyond depths which the 
human mind is utterly unable to conceive there come to 
us the rays of light which myriads of those orbs are pour- 
ing forth, and it is from the lessons taught us by these 
light-rays that we are to form our ideas concerning the 
nature of the orbs which emit them. Yery carefully 
and cautiously must we proceed, if we would avoid being 
led into vain imaginings. It will but mislead us to pass 
a single step beyond the path which is dimly lighted for 
us, and yet that path is so narrow and so obstructed with 
difficulties that we find ourselves continually tempted 
to leave it, and to venture forward on the alluring and 
easy paths which speculation opens out on every hand 
around us. 

And yet we may well remain content to listen only to 
the teachings of known facts. Even so restraining our- 



OTHER 8UNS THAN OURS. 233 

selves, we have in reality a wide and noble domain to ex- 
plore. Facts which seem severally unimportant, are found, 
when considered as parts of a grand whole, to indicate re- 
lations so impressive and so interesting that the revela- 
tions of the telescope within the solar system are apt to 
seem commonplace beside them. "We have, in fact, no 
longer to consider the structure of a system — the archi- 
tecture of the universe is our theme. 

Let us examine carefully the evidence which science 
has gathered together for us, endeavoring at each step to 
gain the full amount of knowledge the several facts in- 
volve, while at the same time cautiously refraining from 
any attempt to overstep the bounds indicated by our evi- 
dence. 

In the first place let us consider what may be learned 
from the analogy of the solar system. The study is an in- 
viting one, since the discoveries on which we are to found 
our views have been made so recently that the subject 
has all the charm of novelty and freshness, while it in- 
volves the consideration of the soundest and most instruc- 
tive mode of pursuing our researches. 

"We have seen in the solar system a variety and com- 
plexity of structure, such as, half a century ago, few as- 
tronomers would have thought of ascribing to it. W r hen 
Sir William Herschel began that noble series of researches 
amid the sidereal depths by which his name has been 
rendered illustrious, he saw in the solar system a scheme 
very different indeed from that which is presented to our 



284 OTHER WORLDS THAN OURS. 

contemplation. He beheld a vast central body, surround- 
ed by a limited number of orbs, some of which are the 
centres of subordinate schemes of greater or less extent. 
When we have added the ring of Saturn as the only for- 
mation differing from planets and satellites in character, 
and the comets, few and far between, which seemed rather 
accidental tributaries of the sun than regular members of 
his family, we have considered all the features which the 
solar system, as known in Sir William Herschel's day, 
presented to the contemplation of astronomers. 

With us it is very different. We see that there exists 
within the solar system a variety of size and structure, of 
motion, arrangement, and aggregation, which is already 
inconceivable, and yet doubtless but faintly shadows 
forth the real complexity and richness of the scheme 
swayed by our sua. Perhaps it is in considering the so- 
lar system in the particular light in which, in this treatise, 
I have had occasion to present it, that this wonderful va- 
riety of conformation is made most strikingly apparent. 
But, apart from all speculative theories, there can be no 
doubt that the solar system presents to us a subject of 
study amazing in itself, but most amazing when we re- 
gard it as supplying the analogies which are to guide us 
in forming our views respecting the sidereal system. Be- 
sides the family of planets circling round the sun, besides 
the system of dependent orbs which circle round the plan- 
ets, we see a zone in which independent planets circle by 
hundreds, perhaps even by myriads 3 around the solar orb ; 



OTHER SUNS THAN OURS. 235 

we see the ring of Saturn composed of thousands of tiny 
bodies ; we see the meteoric systems in countless hosts ; 
we see the comets of our scheme in millions on millions ; 
and less certainly, but still not indistinctly, we recognize 
the existence of a multitude of new and hitherto unsus- 
pected forms of matter within the circle of our sun's at- 
traction. 

What opinion then are we to form — even here, at the 
Very outset of our inquiry — respecting the sidereal scheme 
of which our sun forms but a unit ? Surely it would be 
to lose sight of the significant lesson taught us by the so- 
lar system, it would be to forget how sure and safe a 
guide the greatest of modern astronomers found in the 
teachings of analogy, to adopt the same view now which 
that great astronomer adopted a century ago. If, viewing 
the solar system as consisting of discrete orbs, compara- 
ble one with another in size, and distributed with a cer- 
tain uniformity around their ruling centre, Sir William 
Herschel held that the sidereal scheme presented some- 
what similar relations, surely we, who know certainly that 
the solar system is constituted so differently, must adopt 
a far different view of the sidereal system also. 

Let us remember that there is here — so far as our re- 
spect and admiration for Sir William Herschel are con- 
cerned — a choice between two courses. Assuming, as in- 
deed is just, that the views of our great men are not rash- 
ly to be thrown on one side, we have to choose whether 
we would rather abandon the views which Sir William 



236 OTHER WORLDS THAN OURS. 

Herschel formed about facts, or the views which he 
formed about principles. If we accept his opinion (or 
rather, after all, his mere suggestion), that the stars are 
tolerably uniform in magnitude and distribution, we must 
abandon the analogy of the solar system. If, on the con- 
trary, we accept Sir William Herschel's often-expressed 
opinion that, in theorizing about the unknown, there can 
be no safer guide than the analogy of known facts, we 
must abandon the view (which seemed to him but prob- 
able) that the stars are distributed with tolerable uniform- 
ity throughout our galaxy, and are comparable inter se in 
magnitude and splendor. 

There can be no doubt which course is preferable. We 
know certainly that Sir William Herschel was often mis- 
taken, as all men must be, in matters of fact ; while we 
know with equal certainty that he owed the marvellous 
success with which he theorized to his adoption of the 
principle that analogy is the chief and the best guide for 
the student of astronomy. 

We are compelled, then, in our very respect and ad- 
miration for the greatest astronomer of modern times, to 
regard the constitution of the sidereal system as, in all 
probability, very different from what he imagined. We 
must be prepared to expect an infinite variety of figure, of 
structure, of motion, and of aggregation throughout the 
galactic scheme. If some orbs within that scheme seem 
probably to be suns like our own, we must not be surprised 
to find others which are probably far larger or far smaller. 



OTHER SUNS THAN OURS. 237 

We may look for objects differing as much from the suns 
of the sidereal system as the asteroidal zone differs from 
Saturn or from Jupiter. So that, if we should recognize 
evidence of the existence of clusters of minute stars — a 
whole cluster, perhaps, not equalling in real importance 
the least of the suns of the system — we may accept that 
evidence without any scruple suggested by the improba- 
bility of the conclusion to which it points. Again, we 
may expect to find schemes within the sidereal system, 
differing as much from discrete stars or star-clusters as 
the rings of Saturn differ from the primary planets or 
from the asteroidal zone. So that, if we should recognize 
evidence of the existence of relatively minute clusters, 
whose components are either so small or so closely aggre- 
gated as not to be separately visible even in our most 
powerful telescopes, this evidence may fairly be accepted 
as accordant with the only analogy we have for our guid- 
ance. Yet once more : we may look for systems differing 
as much from all ordinary star-clusters as the eccentric 
and far-reaching meteor systems differ from the symmetri- 
cal rings of Saturn. So that, if we should find evidence 
of strange schemes within the sidereal system, schemes 
presenting strange varieties of figure, with strange com- 
plexities of spiral whorls or outlying branches, losing 
themselves, as it were, in the depths toward which they 
seem to extend — this also need not surprise us : we need 
not conclude that here, at any rate, we are looking beyond 
the bounds of the sidereal system, and gazing upon 



238 OTHER WORLDS THAN OURS. 

external galaxies ; for the analogy we have chosen foi 
our guidance teaches us that such structures were to be 
expected within the scheme of which our sun is a com- 
ponent. And finally, if we should find reason to assure 
ourselves that there are objects in the depths of space 
whose very substance and constitution are different from 
those of all other objects within the sidereal system, we 
need by no means believe that the objects thus singularly 
constituted belong to or form external systems. For the 
millions on millions of comets which form part and parcel 
of the solar system present a precisely analogous differ- 
ence of structure, as compared with the other members of 
that system. 

Having thus replaced the erroneous analogies to which 
■ — through no fault of his own — Sir "William Herschel was 
led to look for guidance, by the more trustworthy analo- 
gies which the recent progress of astronomy has afforded 
for our instruction, we may proceed to consider the direct 
evidence we have respecting the constitution of our galaxy. 

In the first place, let us examine the evidence pointing 
to the dimensions of the sidereal system. 

That the nearest members of the system lie at enormous 
distances from us is proved by the fact that, as the earth 
sweeps on her vast orbit round the sun, no appreciable 
change is observed in the configuration of the star-groups. 
That a circle having a diameter of more than 185,000,000 
of miles should be swept out year by year as the earth 
traverses her orbit, and yet that the surrounding stars 



OTHER SUNS THAN OURS. 239 

should exhibit no change of place, is at once the most 
striking and the simplest evidence we have of the enor- 
mous scale on which the sidereal system is constructed. 
And yet this first obvious fact sinks almost into insig- 
nificance when we regard thoughtfully the teaching of 
modern instrumental astronomy. There might be a real 
shifting of apparent position which yet the unaided eye 
would fail to detect, and such a change would indicate 
distances so enormous that the mind fails altogether to 
conceive their real significance. But the exact instru- 
ments of modern times would exhibit a change of place 
far more minute than any which the unaided eye could 
recognize. If a star shifted by so much as the ten- 
thousandth part of the moon's apparent diameter, modern 
astronomers could assure themselves of the change of 
place. And when we remember that in precisely the 
same proportion that we increase the exactitude of instru- 
mental observation we increase also the significance of 
the stars' apparent fixity of position, it will be seen at 
once how astounding is the lesson conveyed by the fact 
that all but a very few indeed of the stars remain abso- 
lutely unaffected — even under the most powerful instru- 
mental examination — by the enormous range of the earth's 
orbital motion. 

We can roughly estimate the distance of the few stars 
which are thus affected, and thence — on the hypothesis 
that the intrinsic brilliancy of their light is the same as 
the sun's —we may form some idea of their dimensions. 



24:0 OTHER WORLDS THAN OURS. 

I shall, however, only apply this process, in detail, to a 
single case, because my present object is rather to indi- 
cate in a general way the scale on which the sidereal 
system is constructed than to enter at length on the more 
exact details which find their place in ordinary treatises on 
astronomy. 

The star Alpha Centauri is one of the brightest in the 
heavens, Sirius and Canopus alone surpassing it in 
splendor. But it was not its exceptional brilliancy alone 
which led astronomers to regard it as likely to afford 
evidence of an apparent change of place corresponding to 
the earth's real change of place as she sweeps round her 
orbit. Of course, the brightest stars are presumably the 
nearest ; but there is another indication of proximity at 
least equally important. The so-called fixed stars are in 
reality slowly moving onward on definite courses — slowly, 
that is, in appearance, though in reality their motions are 
doubtless inconceivably rapid. Now these motions, the 
proper motions of the stars, as they are called, are as yet 
very little understood. We know only that the whole of 
the galactic system is astir with life, but whither the orbs 
are severally tending we are not yet able to say. Nor do 
we know what portion of the stellar motions may be due 
to the undoubted proper motion of our own sun through 
space. 

This, however, may be regarded as certain, that until 
we know something respecting the laws which regulate 
the stellar movements we must regard the magnitude of a 



OTHER SUNS TBAN OURS. 241 

star's motion as probably an indication of relative prox- 
imity. Precisely as a man walking at a great distance 
from us appears to move much more slowly than one 
who is walking at the same rate close by, so the apparent 
rate of a star's motion is diminished in proportion to the 
star's distance from us. When, therefore, it was found 
that the star Alpha Centauri is moving more rapidly than 
other stars, this fact, combined with the great lustre of 
the star, led astronomers to suspect that it must be com- 
paratively near to us. 

Observations made to determine whether the star 
shows any sign of an annual change of place correspond- 
ing to the earth's annual orbital motion, were rewarded 
by the detection of a very appreciable displacement. In 
fact, owing to the motion of the earth, each year, in a 
nearly circular orbit 185,000,000 miles in diameter, the 
star Alpha Centauri appears to trace out each year a mi- 
nute oval path on the celestial sphere, the greater axis of 
the oval being equal in length to about T ^th part of the 
moon's apparent diameter.* 

It follows from this that in round numbers the dis- 
tance of Alpha Centauri from us is about twenty millions 
of millions of miles. The distance of the earth from the 
sun shrinks into insignificance beside this enormous gap. 

* It hardly need be mentioned, perhaps, that this motion being su- 
peradded to the star's more considerable proper motion, the path which 
the star seems really to follow is a looped one, the size of each loop be- 
ing small in comparison with the distance between successive loops. 
16 



242 OTHER WORLDS THAN OURS. 

Even Neptune, though circling round the sun at a dis- 
tance thirty times vaster than that which separates us 
from that luminary, is yet relatively so much nearer than 
Alpha Centauri, that a sun filling the whole orbit of Nep- 
tune would appear, as seen from that star, but about 
•g-J-^th as large as the sun appears to us. 

Now let us consider what dimensions we may assign to 
Alpha Centauri, on the assumption that the surface of 
this star emits a light as brilliant as that which proceeds 
from the photosphere of our own sun. We must not neg- 
lect the consideration that the star is double — the com- 
panion emitting perhaps about one-sixth as much light as 
the primary.* The distance of Alpha Centauri is equal 
to about 230,000 times that which separates us from the 
sun. Therefore, if removed to the star's distance, the sun 
would shine with only 3-2-g~oTroTro"oo"oth part of his present 
brilliancy. Now, according to the most careful estimates 
of the brilliancy of Alpha Centauri, the light we receive 
from that star is about TpxoooTnroTrth of that we receive 
from the sun.f It follows, therefore, that the star emits 

* In the first edition of this work the smaller star was described as 
emitting about one- sixteenth as much light as the primary; and in a 
note I remarked that Sir John Herschel, observing the star with his 20- 
foot reflector, thought the secondary brighter than it is usually consid- 
ered, but that, for a comparison of this sort, smaller telescopes seemed 
to me likely to be on the whole more trustworthy. He convinced me 
that my opinion as to the brightness of the secondary was erroneous. 
Hence the change in the estimate. 

•f- This estimate is founded on Sir John Herschel's comparison between 
the light of the star and that of the full moon, and Zollner's compari- 
son between the light of the full moon and that of the sun. 



OTHER SUNS THAN OURS. 243 

about three times as much light as the sun ; and there- 
fore, so far as the emission of light is a criterion of size, 
the star may be regarded as considerably larger than our 
own sun. In fact, reducing the total light of the pair by 
one-seventh, we find that the primary must still emit 
nearly three times as much light as the sun, and there- 
fore the diameter of the star, as thus estimated, would 
appear to exceed our sun's in the proportion of about 8 
to 5. 

We have here, then, clear and decisive evidence in favor 
of the view that among the fixed stars there are orbs 
which may be regarded as veritable suns worthy to be 
the ruling centres of schemes as noble as the solar sys- 
tem. For we know quite certainly that the greater num- 
ber of the first-magnitude stars are very much further 
from us than Alpha Centauri, with which, however, they 
are fairly comparable in brilliancy ; so that they may be 
regarded as for the most part at least equal to that star 
in size and mass. Sirius and Canopus, indeed, must far 
surpass Alpha Centauri. The latter, though more than 
thrice as bright, exhibits no appreciable change of posi- 
tion as the earth circles round the sun. Sirius, which is 
more than four times as bright as Alpha Centauri, shows 
an annual change of position which certainly does not 
exceed one-fourth of that star's. It is therefore four 
times further from us than Alpha Centauri, and, did it 
emit no greater amount of light, would appear to shine 
with but one-sixteenth of that star's lustre. As in reality 



244 Of HEM WOMLDS THAN OURS. 

it is four times as bright, the real amount of light it 
emits must exceed that of Alpha Centauri no less than 
64 times, and that of our own sun no less than 192 times. 
So that, judged from this indication alone, the diameter 
of Sirius may be held to exceed that of our sun in the 
proportion of about 14 to 1, an estimate which assigns 
to Sirius a diameter of nearly 12,000,000 miles, and a 
volume 2,688 times as large as the sun's. 

But on the other hand, still confining our attention to 
this method of estimating magnitude, we find reason for 
believing that many of the visible stars must fall far 
short of our sun in magnitude. The sixth-magnitude 
double star 61 Cygni has been found to be nearer to us 
than Sirius, and about three times as far from us as 
Alpha Centauri. Now, we may assume that each compo- 
nent sends us about one-hundredth part of the light we 
receive from Alpha Centauri : it follows that the latter 
star, if removed to the distance at which 61 Cygni lies 
from us (when its light would of course be dimin- 
ished to one-ninth of its present value), would out- 
shine either component of that double star more than 11 
times. Hence (on the assumption that brightness is a 
fair measure of real dimensions), each component has a 
diameter less than one-third that of Alpha Centauri. We 
may roughly estimate the volume of each at about one- 
thirtieth of that of the latter star. So that, remember- 
ing what has already been shown respecting the relation 
between Alpha Centauri and our sun, the two suns which 



OTHER SUNS THAN OURS. 245 

form the double star 61 Cygni would each have a diame- 
ter equal to about seventeen-thirtieths of the sun's, and a 
volume equal to about two-elevenths of his. The sum of 
their volumes would be therefore about one-third of his ; 
and it will presently appear that a perfectly distinct 
method of estimation tends to show that the sum of their 
masses bears about the same proportion to the sun's 
mass. 

But here at once we have evidence that there is a very 
wide range of magnitude among the fixed stars. We have 
seen reason to believe that Sirius is 2,688 times as large 
as the sun, while each of the suns forming the double 
star 61 Cygni would appear to have a volume less than 
one-fifth of our sun's, and therefore less than yg-J^ths °^ 
the volume of Sirius. So that, by considering only three 
cases, we have found tolerably clear evidence of a range 
of variety in volume, reminding us forcibly of that which 
we recognize in the solar system. We cannot suppose 
that these three cases, which have been selected at ran- 
dom — so far as the question of volume is concerned — in- 
dicate anything like the real limits within which the 
fixed stars differ in magnitude. So that we may confi- 
dently accept, as the most probable conclusion from the 
evidence before us, that the range of real magnitude 
among the fixed stars is very far greater than Sir W. 
Herschel was led to anticipate when, nearly a century 
ago, he began his researches into the sidereal system. 

But it is not sufficient that we should thus form an es- 



246 OTHER WORLDS THAN OURS. 

timate of the nature of the fixed stars from the amount of 
light they send to us. It is desirable — and fortunately it 
is practicable — to obtain information as to the absolute 
mass or weight of some of the fixed stars, and further, to 
ascertain of what substances they may be composed, and 
in what condition those substances may exist. Mere 
lights, however glorious, or however wide the sphere 
within which they displayed their splendors, would not 
be fit to sway the motions of orbs resembling those whish 
circle around our sun. Nor would such lights serve to 
indicate to the astronomer that, out yonder, myriads of 
millions of miles beyond the extreme limits of the solar 
system, there exist materials suited to form the substance 
of worlds resembling our own. 

It seems a strange circumstance that astronomers 
should be able to form a more exact and trustworthy es- 
timate of the weight of certain fixed stars than they can 
hope to form respecting the volume of any of those 
bodies. 

Let us consider the evidence. 

I have spoken of the star 61 Cygni as a double star. 
The smaller star shows very clear indications of orbital 
motion around its primary. That the two are associated 
together, and not merely seen (as it were by accident), 
nearly in the same line of view, is indeed certain, because 
that peculiarly large proper motion already referred to is 
shared in by both. But many stars may be physically 
associated, and yet the distance really separating them 



OTHER SUNS THAN OURS. 247 

may enormously exceed that by which they seem to be 
separated — since the line joining them is not necessarily 
square to the line of sight. The components of the stai 
61 Cygni have been carefully watched, however, and 
their motions show that they are circling round each 
other in a plane nearly square to the line of sight. The 
distance separating them is probably about half as large 
again as the distance of Neptune from the sun. 

The period of revolution appears to be about 520 years, 
wlr sh is more than three times as great as the period of 
Neptune. Now we know that a planet, placed at a dis- 
tance from the sun equal to that which separates the 
components of 61 Cygni, would occupy a much less 
period than 520 years in completing a revolution ; in fact, 
its perLd would be about 300 years. Hence it follows 
that the components of 61 Cygni are attracted together 
less forcibly than Neptune is attracted toward the sun, 
and therefore that the sum of their masses must be less 
than the sun's mass. It is easy to compute the actual 
proportion, and we find, on doing this, that the two com- 
ponents of 61 Cygni, taken together, weigh about one- 
third as much as our sun.* 

The star Alpha Centauri is also a binary system, and 
though it has not been so systematically observed as 61 

* It may be easily shown that if a pair of bodies circling around eaoh 
other at a certain distance take a certain time T in effecting a revolu- 
tion, while another pair at the same distance take a time t, the former 
pair, taken together, have a weight which bears to the weight of the 
latter pair the ratio of P to T 2 . 



248 OTHER WORLDS TEAtf OURS. 

Cygni, some astronomers believe that its period has beeu 
even more satisfactorily determined. Indeed there are 
peculiarities in the motion of 61 Cygni which, without 
throwing doubt on the general conclusions deduced above, 
yet suggest that a third (probably opaque) orb affects the 
motions of the other two. From a careful comparison of 
all the observations made in recent times on Alpha Cen- 
tauri, Mr. Hind has assigned to the components a period 
of revolution of about eighty-one years, and a mean dis- 
tance of 13.6 seconds of arc, corresponding to a real dis- 
tance exceeding the earth's distance from the sun some fif- 
teen times. Since a planet placed at this distance from the 
sun would occupy less than sixty years in completing a 
revolution round that body, it follows that the mass of 
the two components of Alpha Centauri must be less than 
that of the sun. This result (if the data be considered 
trustworthy) would indicate a considerable difference be- 
tween the condition of the star and that of our sun ; for 
we have seen that the star gives out much more light 
than the sun. However, I believe that many years must 
elapse before we can regard the period of Alpha Centauri 
as satisfactorily determined.* 



* Mr. Powell supplies the most satisfactory elements of the orbit yet 
given, since he founds his estimate on a more complete series of obser 
vations. He assigns to the system a period of 76£ years, and a mean 
distance of 20.13 seconds of arc, corresponding to a real distance about 
22 times as great as the earth's distance from the sun. A planet at this 
distance from the sun would occupy about 103 years in completing a rev- 
olution. Henee the mass of the two components of Alpha Centauri 



OTHER SUNS THAN OURS. 249 

Still, we have conclusive evidence in this case, as in 
that of the star 61 Cygni, that the component stars are 
really bodies of enormous weight, and consequently well 
fitted to sway the motions of families of planets. We 
conclude, therefore, that the fixed stars generally are 
suns, not mere lights ; and further, we are led to believe 
that there must be a general similarity in the conditions 
under which these bodies and our own sun emit light. 
And thus we are led to recognize other stars also — though 
yet unweighed — as massive orbs, not merely supplying 
light to other worlds travelling around them, but regulat- 
ing by their attractive influences the orbital motions of 
their dependent worlds. 

But we owe to the revelations of the spectroscope the 
complete proof of these matters, besides evidence on 
other and equally interesting points. 

It had long been known that the spectra of the fixed 
stars present a general resemblance to the solar spectrum, 
though of course very much fainter ; and that dark lines 
can be seen in these spectra, some of which correspond 
with those in the sun's spectrum while others seem to be 



turns out to be greater than that of the sun — instead of less, as when 
Mr. Hind's elements were used. This corresponds with the measure- 
ment of the star's light, though the disproportion of the masses calcu- 
lated in this way is not so considerable as it would be if the masses 
were inferred from the light of Alpha Centauri. By applying the for-. 
mula of t\ie preceding note, it will easily be found that with Mr. Powell's 
elements the mass of Alpha Centauri (both components) equals about 
twice that of our sun. 



250 OTHER WORLDS THAN OURS. 

new. So soon as the great discovery effected by Kirch- 
hoff had been announced, it was seen at once that these 
dark lines in the stellar spectra afford the means of de- 
termining the constitution of the stars. It was only nec- 
essary that these lines should be identified by their cor- 
respondence with the lines belonging to known elements, 
in order to prove that these elements exist in the sub- 
stance of the star. But although the principle on which 
researches were to be conducted was sufficiently simple, 
many difficulties had to be encountered. Indeed, the at- 
tempts made by Airy, Secchi, and Rutherfurd to solve 
the problem of determining the constitution of the stars 
by means of spectroscopic analysis were unsuccessful ; 
and it was not until Mr. Huggins and Professor Miller 
commenced their famous series of researches that the 
problem can be said to have been fairly mastered. 

Even in the hands of these eminent physicists the 
work was difficult and its progress tedious. The weather 
necessary for the successful prosecution of so delicate a 
method of inquiry does not often prevail in our variable 
climate. The comparison between the dark lines in the 
stellar spectra and the bright lines belonging to various 
elements was not only a delicate and laborious task, but 
was singularly painful to the eyes. And other difficulties 
into which I have not space to enter here had to be en- 
countered and overcome. 

But undeterred by these difficulties, the two physicists 
persevered in their researches, and were rewarded by re- 



OTHER SUNS THAN OURS. 251 

suits so interesting and important that their discovery 
may be said to constitute the most remarkable era in the 
history of sidereal research since the completion of the 
star-gangings of the elder Herschel. 

Two bright stars, Betelgeux, the leading brilliant of 
Orion, and Aldebaran, the chief star of Taurus, were ex- 
amined with special care. Mr. Huggins remarks that the 
spectra of these stars are as rich in lines as the solar spec- 
trum itself. The places of no less than eighty lines in 
the spectrum of Betelgeux were accurately measured, 
while as many as seventy lines had their places assigned 
to them in the spectrum of Aldebaran. 

With respect to the former spectrum, Mr. Huggins re- 
marks that it is most complex and remarkable. " Strong 
groups of lines are visible, especially in the red, the green, 
and the blue portions ; " a peculiarity, it may be remarked 
in passing, which serves to account for the well-marked 
orange color of this star. 

Now here already we have very decided evidence as to 
the nature of the star ; since the very fact that its spec- 
trum presents the same general appearance as the solar 
spectrum proves conclusively that the star is an incan- 
descent body, whose light comes to us through certain 
vapors corresponding to those which surround the sun. 
Nor should we be able to regard the star as other than a 
sun, even' though none of the elements known to us should 
appear to be present in its substance or in the vapors sur- 
rounding it. For clearly we have no reason for believing 



252 OTHER WORLDS THAN OURS. 

that worlds can be formed out of those elements onty 
with which we are acquainted, unless we find as we pro- 
ceed that those elements actually do compose the suns 
which form the sidereal system. Of course, if this shall 
appear to be the case, our conclusions respecting thd 
nature of the stars will be very much strengthened. 

Now, when Professor Miller and Mr. Huggins compared 
the lines in the spectrum of Betelgeux with the bright 
lines of certain terrestrial elements, they found that some 
of these elements do actually exist in the vaporous enve- 
lope of the stars. ' Thus sodium, magnesium, calcium, 
iron, and bismuth are present in Betelgeux. The lines of 
hydrogen, which are so well marked in the solar spectrum, 
are not seen in the spectrum of Betelgeux. We are not 
to conclude from this that hydrogen does not exist in the 
composition of the star. We know that certain parts of 
the solar disk, when examined with the spectroscope, do 
not at all times exhibit the hydrogen lines, or may even 
present them as bright instead of dark lines. It may well 
be that in Betelgeux hydrogen exists under such condi- 
tions that the amount of light it sends forth is nearly 
equivalent to the amount it absorbs, in which case its 
characteristic lines would not be easily discernible. In 
fact, it is important to notice generally that while there 
can be no mistaking the positive evidence afforded by the 
spectroscope as to the existence of any element in iron or 
star, the negative evidence supplied by the absence of 
particular lines is not to be regarded as decisive. 



OTHER SUNS THAN OURS. 253 

In the case of Aldebaran the two physicists were able 
to establish the existence of sodium, magnesium, hydro- 
gen, calcium, iron, bismuth, tellurium, antimony, and mer- 
cury in the vapors surrounding the star. 

Besides these stars fifty others were examined. The 
brilliant Sirius exhibits a spectrum of great beauty, though 
the low altitude which this star attains in our latitudes 
renders the observation of the finer lines exceedingly dif- 
ficult. But the two physicists were able to show that so- 
dium, magnesium, hydrogen, and probably iron, exist in 
this gigantic sun. 

All the stars examined exhibit spectra crossed by nu- 
merous lines, and in a great number of the spectra lines 
belonging to known terrestrial elements were detected. 

And now let us consider the general bearing of these 
interesting discoveries. 

In the first place, we are forced to recognize in the stars 
real suns, not mere lights. Doubtless Whewell did well 
in pointing out that astronomers had no right to regard 
the stars as suns until they had some evidence that these 
orbs resemble the sun in other respects than in size, mass, 
or luminosity. And as in his day it appeared altogether 
unlikely that such evidence should be obtained, a real 
limit seemed placed to the speculations which men might 
form as to the existence of other planetary systems be- 
sides those circling around the sun.' 

But now we have precisely that evidence which Whew- 
ell required. We see that the stars are constituted in 



254 OTHER WORLDS THAN OURS. 

the same general way as the sun, and that further they 
even contain elements identical with those which exist in 
his substance. There is not indeed in every case, per- 
haps there may not be in any case, an exact identity of 
composition between the stars and our sun, or between 
star and star. But this was no more to have been looked 
for than an exact identity of physical habitudes among 
the members of the solar system. That general resem- 
blance of structure which indicates a general resemblance 
in the purposes which the celestial bodies are intended to 
subserve, is undoubtedly evident when we compare the 
stars either with our sun or with each other. 

I have already spoken of the conclusions to be drawn 
from the existence of the same materials in the substance 
of the sun that exist around us on this earth. I have 
shown that we are compelled to regard this general re- 
semblance of structure as sufficient to prove that the 
other planets resemble the earth, since we have no reason 
to believe that our earth bears an exceptionally close re- 
semblance to the sun as respects the elements of which 
she is composed. 

Since, then, we have reason to believe that all the plan- 
ets which circle around the sun are constituted of the 
same materials which exist in his substance, though these 
materials are not necessarily nor probably combined in 
the same proportions throughout the solar system, we 
have every reason which analogy can give us for believ- 
ing that the planets circling around Betelgeux or Aide- 



OTHER SUNS THAN OURS. 255 

baran are constituted of the same materials which exist 
in the substance of their central luminary. 

Thus we are led to a number of interesting conclusions 
even respecting orbs which no telescope that man can 
construct is likely to reveal to his scrutiny. The exist- 
ence of such elements as sodium or calcium in those other 
worlds suggests the probable existence of the familiar 
compounds of these metals — soda, salt, lime, and the rest. 
Again, the existence of iron and other metals of the same 
class carries our minds to the various useful purposes 
which these metals are made to subserve on the earth. 
"We are at once invited to recognize that the orbs circling 
around those distant suns are not merely the abode of 
life, but that intelligent creatures, capable of applying 
these metals to useful purposes, may exist in those worlds. 
"We need not conclude, indeed, that at the present mo- 
ment every one of those worlds is peopled with intelligent 
beings, because we have good reason for believing that 
throughout an enormous proportion of the time during 
which our earth has existed as a world no intelligent use 
has been made of the supplies of metal existing in her 
substance. But at some time or other those worlds have 
been or will be the abode of intelligent creatures seems 
to be a conclusion very fairly deducible from what we 
know of their probable structure. 

But secondly, apart from the information afforded by 
the spectroscope respecting the materials of which the 
stars are composed, the nature of the stellar spectra 



256 OTHER WORLDS THAN OURS. 

serves to prove most conclusively that the stars, besides 
supplying light to the worlds which circle around them, 
radiate heat also to them. Even if we were not certain 
that elements which are only vaporized at a very high 
temperature exist in the vaporous envelopes of the stars, 
yet the very nature of the light sent out by the stars in- 
dicates that these orbs are incandescent through intensity 
of heat. "When we find that the spectrum of the moon's 
light resembles the solar spectrum, we do not indeed con- 
clude that the moon is as intensely heated as the sun, be- 
cause we know that the moon is not self-luminous. But 
in the case of self-luminous bodies like the stars, we can 
conclude from the very nature of their spectra that these 
orbs are intensely heated. Of course we are rendered ab- 
solutely certain of this when we find that iron and other 
metals exist in the form of vapor in the stellar atmos- 
pheres. 

The vast supplies of heat thus emitted by the stars not 
only suggest the conclusion that there must be worlds 
around these orbs for which those heat-supplies are in- 
tended, but point to the existence in those worlds of the 
various forms of force into which heat may be trans- 
muted. We know that the sun's heat poured upon our 
earth is stored up in vegetable and animal forms of life ; 
is present in all the phenomena of nature — in winds, and 
clouds, and rain, in thunder and lightning, storm and 
hail ; and that even the works of man are performed by 
virtue of the solar heat-supplies. Thus the fact that the 



OTHER SUNS TBAN OURS. 257 

stars send forth heat to the worlds which circle around 
them suggests at once the thought that on those worlds 
there must exist vegetable and animal forms of life ; that 
natural phenomena, such as we are familiar with as due 
to the solar heat, must be produced in those worlds by 
the heat of their central sun ; and that works such as 
those which man undertakes on earth — works in which 
intelligent creatures use Nature's powers to master Nat- 
ure to their purposes — may go on in the worlds which 
circle around Aldebaran and Betelgeux, around Vega, 
Capella, and the blazing Sirius. 

Recently it has even been found possible to render the 
stellar heat sensible to terrestrial observation — by methods 
which need not here be inquired into. Nay, the task of 
measuring the amount of heat received from certain stars 
has not been thought too difficult. Mr. Stone, making 
use of the powers of the great equatorial of the Green- 
wich Observatory, and ingeniously overcoming the numer- 
ous difficulties which exist in a research of such exceeding 
delicacy, has arrived at the conclusion that Arcturus sends 
us about as much heat as would be received from a three- 
inch cube full of boiling water, and placed at a distance 
of 383 yards. Yega, which shines, according to Sir J. 
Herschel, with about two-thirds the light of Arcturus, 
gives out about the same proportionate amount of heat.* 

* Although these results cannot yet be regarded as numerically ex- 
act, it may be interesting to consider the amount of heat given out by 
Arcturus in relation to the light sent us by this star, the more so as 
17 



£58 OTHER WORLDS THAN OURS. 

But in other instances the heat-giving power of a star has 
not been found proportional to the amount of light it 
emits. 

The variation of many fixed stars in lustre at once 
forms a new bond of association between the stars and 
the sun — which we have seen to be in reality a variable 
star—and suggests interesting inquiries as to the ex- 
istence of variation in the emission of heat. Some of 
the stellar variations of light are so much more marked 
than those noticed in the case of our own sun that we can 
scarcely conceive how creatures resembling any with 
which we are acquainted could endure the effects of cor- 
respondingly important variations of heat ; nay, in some 
instances we seem compelled to withhold our belief in 
the existence of habitable systems around certain fixed 
stars. The star Eta Argus, for example, which some- 
times blazes out with a light surpassing that of any of 
the stars in the northern hemisphere, while at other 
times it falls to the sixth magnitude, can hardly be re- 

this star seems (from the nature of its spectrum) to resemble the sun 
very closely in constitution. The light sent to us by Arcturus is equal 
to about three-fourths of that supplied by Alpha Centauri, or about 
rnnrooooo until part of the light we receive from the sun. Now Mr. 
Stone estimates the direct heating effect of Arcturus at 0.00,000,127° 
Fah., making due allowing for the effect of the object-glass in concen- 
trating and absorbing the heat. It will be seen at once that, according 
to this estimate, the heating power of Arcturus bears a very much 
greater proportion to that of the sun than the respective light-giving 
powers of the luminaries bear to each other. This seems to throw some 
doubt on the correctness of the estimate either of the light-giving or of 
iba beat-giving power of the star. 



OTHER SUNS THAN OURS. 259 

garded as fit to be the centre of a system of worlds. I 
pass over such variable stars as the one which recently 
blazed out in the Northern Crown, because in a case of 
this sort the star may be regarded as really a small orb, 
and its sudden lustre is due to some exceptional occur- 
rence, leading (as the spectrum of the star seemed to 
show) to a temporary conflagration. But Eta Argus and 
Mira Ceti seem to belong to a different category alto- 
gether, since it is probable as respects the former, and 
certain as respects the latter, that their appearance as 
stars of the leading magnitude is not accidental, but part 
of a systematic series of changes. 

It remains only to be mentioned that, besides light and 
heat, the stars emit actinic rays. This is proved de- 
cisively by the fact that the stars can be made to photo- 
graph themselves. It has been found, however, that the 
actinic power of a star, like its heat-giving power, is not 
by any means proportional to the star's light. So that 
in this respect, as in the material constitution of the 
stars, we find specific varieties even amid those very 
features which indicate most strikingly the general re- 
semblance which exists between the suns constituting 
the sidereal system. 

To sum up what we have learned so far from the study 
of the starry heavens — we see that, besides our sun, there 
are myriads of other suns in the immensity of space ; that 
these suns are large and massive bodies, capable of sway- 
ing by their attraction systems of worlds as important as 



'260 OTHER WORLDS THAN OURS. 

those which circle around the sun; that these suns :Z3 
formed of elements similar to those which constitute ou>r 
own sun, so that the worlds which circle round them may 
be regarded as in all probability similar in constitution 
to this earth ; and that from these suns all the forms of 
force which we know to be necessary to the existence of 
organized beings on our earth are abundantly emitted. It 
seems reasonable to conclude that these suns are girt 
round by dependent systems of worlds. Though we can- 
not, as in the case of the solar system, actually see such 
worlds, yet the mind presents them before us, various in 
size, various in structure, infinitely various in their 
physical condition and habitudes. 



MINOR STABS. 261 



CHAPTEE XL 

OF MtM)E riTAftS, AND OF THE DISTRIBUTION OF STARS IN 

SPACE. 

It has been so long a received opinion that a general 
uniformity of magnitude and distribution characterizes 
the stellar system that it is with some diffidence I ven- 
ture to express a different view. And here let me not be 
misunderstood. I am fully sensible that it is only in cer- 
tain popular treatises of astronomy that a belief in any- 
thing like a real uniformity of structure in the sidereal 
system is attributed to astronomers of authority. It is 
not any such imaginary theory that I have now to deal 
with, however; but with opinions which have found a 
place in the works of astronomers from whom I very un- 
willingly differ. 

I propose to exhibit the reasons which have led me to 
believe that, so far from knowing the real figure of the 
sidereal system, astronomers have not been able to pene- 
trate to its limits in any direction ; that leading stars, 
such as those discussed in the preceding chapter, are dis- 
tributed throughout space to the very furthest limits and 
beyond the very furthest limits that our most powerful 
telescopes can attain to ; that the stars are arranged in 



262 OTHER WORLDS THAN OURS. 

groups and clustering aggregations, in streams and whorls 
aud spirals, in a manner altogether too complex for us to 
hope to interpret ; and that in these aggregations stars of 
all degrees of real magnitude are mixed up, from suns as 
large as Sirius down to orbs which may be smaller than 
any of the primary planets of the solar system. 

Let us consider step by step the evidence we have on 
these points. 

"We know, from the existence of double, triple, and 
multiple stars, in which the components are often very 
unequal in splendor, that combinations of stars exist in 
which one or two may be suns like our own, while the 
rest, or some of the rest, are relatively minute. This, 
however, has of course long been known ; and it is only 
as a preliminary step in the investigation that I here ad- 
vance so trite an instance. 

Next let us consider such star-clusters as contain orbs 
of the eighth or ninth magnitude, besides a multitude of 
minute stars. These clusters must of course be regarded 
as lying within the sidereal system, since no external gal- 
axies could reasonably be supposed to contain orbs so in- 
finitely transcending even Sirius in magnitude as to shine 
from beyond the enormous gap separating us from such 
galaxies with a light exceeding that derived from many 
stars within the sidereal system. Now, regarding thase 
clusters as forming part and parcel of the sidereal system, 
we find in the existence of multitudes of minute orbs 
within their range a proof that diversity of magnitude in 



MINOR STABS. 263 

schemes of associated stars is to be regarded as a feature 
of certain parts, at any rate, of our galaxy ; and we shall 
therefore be less surprised if we should find reason for 
believing that it is a characteristic peculiarity of the ga- 
lactic system. 

Now with regard to the nebulae (resolvable and irresolv- 
able), and their claim to be regarded as external galaxies, 
I shall have much to say further on ; but I may remark 
in passing that we have precisely the same reason for 
believing that many of these objects lie within the range 
of the solar system, as have been already considered in 
the case of star-clusters. Their component stars, to be 
visible at all, must fall within the range of distance which 
astronomers have assigned to the boundaries of the gal- 
axy, since some stars even within this range cease to be 
separately visible in the most powerful telescopes man 
has yet constructed. So that when in these objects we 
see a few or many distinct stars, and a mass of nebulous 
light which we judge to proceed from an indefinitely 
large number of minute stars, we again have very decided 
evidence of the fact that in one and the same region of the 
sidereal system there may exist leading stars (so to speak) 
and innumerable stars relatively minute. 

With considerations such as these (and I might add 
many others) to guide us, let us proceed to examine the 
teachings of the Milky Way itself, that we may see 
whether that wonderful zone indeed represents, as has 
been thought, the sidereal system itself, or only an aggre- 



£64 OTHER WORLDS THAN OURS. 

gation of minute orbs altogether insignificant separately, 
in comparison with our sun or Sirius, Aldebaran or Betel- 
geux, Yega or Arcturus. 

The star-gauging of Sir W. Herschel, interpreted ac- 
cording to his hypothesis of stellar distribution, pointed 
to an extension of the Milky Way laterally to a distance 
exceeding some eighty times that which separates us 
from the first-magnitude stars. So that, regarding sixth- 
magnitude stars as on the average about ten times as far 
from us as those of the first magnitude (the usual esti- 
mate), we see that the outermost parts of the galaxy must 
lie (according to Sir W. Herschel's theory) about eight 
times as far from us as the sphere of the sixth-magnitude 
stars. Now Sir John Herschel was led by his observa- 
tions of the southern heavens to so far modify his 
father's theory as to describe the Milky Way as probably 
shaped like a flat ring, the stars down to the tenth mag- 
nitude being in a sense dissociated from the ring, while 
he regarded the probable distance of the outermost limits 
of the ring as 750 times instead of but 80 times the mean 
distance of the first-magnitude stars. This difference of 
opinion, it may be remarked, though obviously not sur- 
prising when we consider the enormous difficulty of the 
problem presented by the sidereal system, is yet suffi- 
cient to indicate the probability that an important error 
has been made in the hypothesis which underlies the 
accepted theories respecting the galaxy. But, be this as 
it may, in regarding the Milky Way as shaped like a flat 



MINOR STABS. 



265 



ring (cloven through one-half of its circumference) whose 
medial section resembles generally the space between the 
dark concentric circles in Fig. 5 (in which S B equals 




Fig. 5.— The Galactic Cloven Flat Ring (Plan). 

eight times S A), I have not adopted a structure which 
exaggerates the difficulties presented by the disk or ring 
theory of the Milky Way. The cross-section would be 
somewhat as shown in Fig. 6. 



LZ 



1 




Fig. 6.— The Galactic Cloven Flat Ring (Section). 



Now, accepting this modified figure, as better according 
with the results of star-gauging than Sir W. Herschel's 



266 OTHER WORLDS THAN OURS. 

theory that the Milky Way forms a cloven disk, let us 
consider whether any peculiarities of the Milky Way 
seem to oppose themselves to this interpretation of its 
structure. 

In the first place, then, there is a gap or rift extending 
right across the single part of the Milky Way in the con- 
stellation Argo ; so that we must conceive that from S 
toward 1, in Fig. 5, the flat ring is broken through by 
some such rift as is indicated by the broken lines in that 
direction. Next there is, in the constellation Crux, a 
pear-shaped vacuity of considerable size, and bounded by 
well-defined edges ; so that we must conceive that from 
S toward 2 (Fig. 5) the flat ring is tunnelled through by 
some such passage as is indicated by the dotted lines in 
that direction. A similar tunnelling, but of different 
cross-section, must exist in direction S 3 (as shown by 
the dotted lines) to account for the dark gap in the con- 
stellation Cygnus. Next, where the Milky Way is 
double, a large portion of one branch is discontinuous, 
so that the upper part of the double portion of the ring 
in Fig. 5 must be supposed removed between the broken 
lines from S to 4 and 5. Over the so-called double 
stream there are in places strange convolutions, in others 
numerous branching and interlacing streams, whose com- 
plexity indeed defies description ; so that the portion 3 
B 2 of the ring must be supposed corrugated in the 
strangest way, and further to throw out plane and curved 
sheets of stars presented tang'entially toward S. Lastly 



MINOR STABS. 267 

the single portion of the Milky Way is very faint indeed 
toward 6, so that here we must conceive its figure 
trenched in upon in the way indicated by the dot-and- 
peck line. 

Thus, even without considering a multitude of minuter 
peculiarities of structure, we are led to the conclusion that 
the Milky Way, judged according to the fundamental hy- 
pothesis of Sir W. Herschel, has some such shape as I 
have endeavored to exhibit in Fig. 7. Although I have 




Ylq. 7. — The Galactic Flat Ring Modified in Accordance with the Observed 
Peculiarities op the Milky Wat. 

not indicated on the figure the corrugations of the ring, 
nor a tithe of the various overlapping layers which would 
be required to account for the appearance of the Milky 
W^ay between Centaurus and Ophiuchus, yet the deduced 
figure is by no means inviting in its simplicity. It is, 
however, absolutely certain that the sidereal system, as 
far as its more densely aggregated star-regions are con- 
cerned, has some such figure as this, if we are to accept 
the principle of Sir W. Herschel's stax-gaugings. 



268 OTHER WORLDS THAN OURS. 

Now, in turning our thoughts to the recognition of a 
more simple explanation of observed appearances, it will 
be well that we should consider some peculiarities of the 
Milky Way which we have not yet attended to. In the 
first place, I would invite attention to a peculiarity ob- 
served by Sir John Herschel in different parts of the gal- 
axy — the fact, namely, that in places the edge of the 
Milky Way is quite sharply defined. One-half of a tele- 
scopic field of view may be quite clear of stars, or show 
only a few straggling orbs, while the other half presents 
what has been called a " Milky Way field " — that is, a 
region profusely sprinkled with stars, the boundary be- 
tween the two portions being well defined. When we see 
that a cluster of objects presents a well-defined edge, 
what conclusion do we draw as to the position of the 
object ? Is it not in such a case absolutely certain that 
the distance of the cluster enormously exceeds the dis- 
tance between its component parts— or in other words, 
that the observer is far outside the cluster ? Many in- 
stances will at once suggest themselves to the reader in 
illustration of this remark. 

We conclude, then, that these portions of the Milky 
Way, at any rate, whether they be regarded as projections 
or nodules, are definite clustering aggregations very far re- 
moved from us. Other parts of the Milky Way may also be 
removed bodily, so to speak, to enormous distances, be- 
cause a cluster which has not a definite edge may be as fat 
removed as one which has ; but certainly those portions are. 



MINOR STARS. 269 

Next let us consider what opinion we may found on 
the existence of dark regions in the Milky Way ; and here 
I refer not merely to such large and obvious vacuities as 
the Coal-sack in Crux or the oval opening in Cygnus, 
but also to small openings, in which, though they occur 
even in rich regions of the Milky Way, there is not, accord- 
ing to Sir W. Herschel's description, even a telescopic 
star to be seen. 

Judged apart from preconceived opinions, such open- 
ings as these, according to all laws of probability, indicate 
that the portion of the Milky Way in which they occur 
has not a very great lateral extension. To return for a 
moment to Fig. 5, it will be seen at once that an aperture 
extending laterally through a star system so shaped must 
have a particular direction and be perfectly straight in 
order to be visible to observers placed, as we are supposed 
to be, in the central opening. It is altogether improbable 
that one such opening should exist by accident, and ab- 
solutely impossible that many should.* We are forced, 
therefore, to infer that, instead of the enormous lateral 
extension assigned to the Milky Way, the galaxy has in 
these places certainly, and elsewhere probably, a lateral 
extension not greatly exceeding its depth. 

* Sir John Herschel distinctly indicated this inference, as he did many 
other matters which make strongly against the received theory of the 
sidereal system. Nor was he unconscious of their bearing. Apparently 
unwilling to press them to their full extent, he was commonly satisfied 
by noting that they do not seem to accord with views he had elsewhere 
dwelt upon. 



270 OTHER WORLDS THAN OURS. 

It is further to be noted that the lucid stars over the 
zone of the heavens which is occupied by the galaxy show 
a very decided preference for the parts of that zone which 
are actually traversed by the Milky Way. For instance, 
we find no stars above the fifth magnitude, and very few 
of these in the Coal-sacks, or in the rift which crosses the 
Milky Way in Argo ; or, again, in the space which lies be- 
tween the two branches where the Milky Way is double. 
If this is an accident it is a very extraordinary one, espe- 
cially when it is remembered that the region where it oc- 
curs is the very part of the heavens where stars of all 
magnitudes may be expected to be most profusely distrib- 
uted ; that the spaces thus left vacant form no inconsid- 
erable aliquot part of that zone ; and that, according to 
the accepted theory, there is no reason for expecting any 
peculiarity of the sort. 

Thus, again, setting aside preconceived opinions, and 
judging only according to the evidence, we seem led to 
regard the coincidence as not accidental,, but as indicating 
that there really is a very close association between the 
bright stars and those small stars forming the milky light, 
which, according to the accepted theory, lie so many times 
further from us. 

But this opinion is absolutely forced upon us when we 
apply a rigid process of examination to the evidence we 
have respecting the distribution of the lucid stars over 
the galactic zone. So far as I am aware, this has not 
hitherto been attempted. Indeed, independently of the 



MINOR STARS. 271 

fact that I have not met with any reference to such an in- 
quiiy, although I have had occasion to study very care- 
fully all the works bearing on the subject, I feel confident 
that the examination I refer to has never yet been at- 
tempted, because I am sure that if it had, the result 
must have been the adoption of views altogether different 
from those at present accepted. I shall have occasion, 
further on, to exhibit the method by which the following 
results have been obtained, and therefore I content myself 
in this place with simply stating them : 

The Milky Way covers ^j-ths of the whole heavens, 
while the gaps and lacunae in the Milky Way cover about 
3^d part. In the Milky Way there are 1,115 lucid stars, 
in the gaps and lacunae only 20. So that if the whole 
heavens were as richly covered with lucid stars as the 
Milky Way, there would be 11,681 stars visible to the 
naked eye, instead of the 5,850 actually seen. But if the 
whole heavens were no more richly strewn with stars than 
the gaps and lacunae in the Milky Way, there would be 
but 1,240 lucid stars. The Milky Way is, in fine, no less 
than nine times as richly strewn with lucid stars as its 
gaps and lacuna?, whereas according to the accepted views 
no such 'peculiarities are to be looJced for in the distribution 
of lucid stai*s over the galactic zone. 

We have here a statistical fact which must be accounted 
for in forming a theory of the sidereal system. I have, 
indeed, no hesitation in saying that it is the most remark- 
able feature of the stellar heavens. No one who appre* 



272 OTHER WORLDS THAN OURS. 

ciates the laws of probability will ascribe it to mere 
chance distribution.* Where, then, is the cause, unless 
we accept the obvious and simple explanation that the 
Milky "Way seems to be thus associated with lucid stars 
because it is associated with them — that in place of being, 
as has so long been supposed, a congeries of suns many 
times more distant than the lucid stars, it is formed of 
myriads of relatively minute orbs compared with which 
those lucid stars are as the giant planets of our solar sys- 
tem compared with the asteroids ? 

It is very clear, then, what views we are to form re- 
specting the Milky Way. If the galaxy is, first, a cluster- 
ing aggregation separated from us by an interval com- 
paratively clear of small stars ; secondly, so shaped thai 
the cross-section of the stream is everywhere not far from 
a roughly circular figure ; and thirdly, associated very 
closely with the bright stars seen in the same field of 
view, then must its structure be somewhat as shown in 
Fig. 8, in which the disks represent lucid stars (very 
much exaggerated of course in size), while the fine dotting 
represents the spiral of relatively minute stars, clustering 
along the spiral group of leading stars. It will be seen 
*it once how, to an observer placed at S, the various feat- 
ires of the Milky Way can be accounted for by this 

* If the clouds of a summer sky arrayed themselves in rank and file 
so as exactly to correspond to the panes of the window through which 
I view them as I write, I should not regard the coincidence as more 
amazing than that involved by the observed relations of the stars if 
these relations are due to chance distribution. 



MINOU STAUS. 273 

figure. Toward a would lie the gap in Argo ; toward b 
two branches, one faint, and in part evanescent through 
vastness of distance, the other forming the brightest part 
of tne spiral ; toward d the projection in Cepheus ; toward 
e the faint part of the Milky Way in Gemini and Mono- 
ceros. The Coal-sacks would be simply accounted for by 
conceiving that branches seen toward the same general 
direction, but at different distances, do not lie in the 




Fig. 8.— The Milky Way Regarded as a Spibai* 

same general plane, and so may appear to interlace upon 
the heavens. We are not only justified in supposing this, 
but forced to do so by the way in which the stream of 
milky light is observed to meander on its course athwart 
the heavens. The branching extensions serve very well 
to account for the appearance of the Milky Way between 
Centaurus and Ophiuchus, where the interlacing branches 
and the strange convolutions and clustering aggregations 
described by Sir John Herschel are chiefly gathered. 
18 t 



274= OTHER WORLDS THAN OURS. 

I would not have it understood, however, that I at all 
insist on the general shape of the spiral shown in Fig. 8. 
On the contrary, that curve is only one out of several 
Which might fairly account for the observed appearance 
of the Milky Way ; and I have often felt inclined to doubt 
whether a single spiral of this sort is in reality the best 
Way of accounting for the observed appearance of the 
galactic zone. What I do insist upon as most obviously 
forced upon us by the evidence is that (1) the apparent 
streams formed by the Milky Way upon the heavens indi- 
cate the existence of real streams in space ; and (2) that 
the lucid stars seen on the stream are really associated 
with the telescopic stars which form, so to speak, the 
body of the stream. Whether that stream form a single 
•spiral or several, or ivhether, instead of spirals, there may 
not be a number of streams of small stars, placed at differ- 
ent distances from us, and lying in all directions round the 
medial plane of the galaxy, but more or less tilted to that 
plane (the sun not lying within any one of the streams), are 
questions which can only be resolved by the systematic 
scrutiny of this wonderful zone. 

The chief points to be noticed among the considerations 
flowing from these general views are these : 

In the first place, the only marked difference between 
the stars of the leading magnitudes (say the first ten) 
lying in the galactic zone, and those lying without it, con- 
sists in the fact that the former are associated with count- 
less multitudes of smaller stars, while the latter appear 



MINOR STARS. 275 

not to have such attendants, or not so many of them. We 
shall see presently that the extra-galactic stars are asso- 
ciated, and in a very intimate manner, with groups of 
very minute stars — of stars so minute indeed as not to be 
separately discernible — so that astronomers have been led 
to regard such groups as external galaxies. But except in 
one region, we do not find outside the galactic zone any 
appearances reminding us of the aspect of the Milky Way 
itself. In that region lie the two Magellanic Clouds, re- 
sembling the Milky Way in their general appearance, but 
seen, when placed under telescopic scrutiny, to differ 
from it in this, that among the minute stars which cause 
the milky light are numbers of nebulae, of classes not 
found commonly, if at all, in the galactic zone. 

In the second place, we must conclude that uncounted 
millions of stars exist which are very minute indeed in 
comparison with those which we have been led to regard 
as suns. That these relatively minute orbs may be abso- 
lutely large — far larger, for instance, than . our own earth 
— may indeed be accepted as certain. But it is difficult 
,to believe that they subserve purposes similar to those of 
our own sun. One cannot but see that orbs such as these 
would not have that permanence of character, as sources 
of heat-supply, which would seem to be necessary in the 
case of a real sun. We know, indeed, that among the 
small stars of the Milky Way there is a proneness to ir- 
regular variation which is not recognized, or is altogether 
exceptional, among the lucid stars. In the neighborhood 



2?6 OTHER WORLDS THAN OtTMS. 

of the Milky Way, with scarcely an exception, those tem- 
porary stars have blazed out which have formed a subject 
of such perplexity to the thoughtful astronomer. Under 
what conditions the small orbs in the Milky "Way actually 
exist, whether clusters of them will eventually segregate 
from their neighbors to form suns, or whether, after long 
voyaging in spiral and contorted paths under the varying 
influences of the attractions of leading stars, these minute 
orbs will, for the most part, be forced to settle down as 
attendants round the major ones, it is as yet altogether 
impossible to judge. It may be that they bear the same 
sort of relation to the leading stars that certain cometic 
and meteoric families, referred to in Chapter IX., bear to 
the major planets of the solar system, not being in any 
case absolutely dependent on any large star, but yet re- 
turning in cycles, which must be measured by millions of 
aeons, to temporary dependence on one sun after another ; 
until in the course of time, under the action of processes 
somewhat resembling those I have conceived to take 
place in the formation of the solar system, the conditions 
under which they move will have become so far altered as 
to lead to the breaking up of the Milky Way into distinct 
systems. Indeed, as Sir William Herschel was led by 
other considerations long since to point out, there, are. 
signs in parts of the Milky Way which would seem to in- 
dicate that several such systems have already reached an 
advanced stage of development. 

But perhaps the most important conclusion deduciHe 



MINOR STARS. 277 

from the circumstances I have dwelt upon (assuming mj 
interpretation of them to be in the main correct) is this, 
that we can no longer suppose we have in any direction 
pierced to the limits of the sidereal system. So long as a 
general approach to uniformity of distribution was under- 
stood to prevail within that system, there was a ready 
means of determining when the telescopist had reached in 
any given direction the limits of the system. To use the 
words of Professor Nichol, " When an eye is directed to- 
ward a prolonged bed of stars, there is no reason to fancy 
that it has reached the termination of that stratum so 
long as there appears behind the luminaries which are 
individually seen any milky or nebulous light ; such light 
probably arising always from the blended rays of remoter 
masses. But if, after struggling long with a nebulous 
ground, we obtain a telescope that gives us additional 
light with a perfectly black shy, we then have every rea- 
son the circumstances can furnish on behalf of the sup- 
position that at length we have pierced through the stra- 
tum ; a probability, indeed, which can be converted into 
certainty in only one way — viz., when no increase of orbs 
follows on the application of a still larger instrument." 
Sir John Herschel has expressed a similar view, and 
there can, indeed, be no doubt that, adopting the funda- 
mental hypothesis on which accepted views are founded, 
the test above described is an absolutely certain one. 

But if, instead of penetrating further and further into 
space when "struggling long with a nebulous ground " 



278 OTHER WORLDS THAN OURS. 

(to use Professor Nichol's striking but somewhat incorrect 
expression), we have in reality only been searching with 
more and more minuteness into a definite cluster or 
stream of stars, we can no longer come to the conclusion 
he has insisted upon. We have reached the limits of 
minuteness which the stars of the cluster or stream attain 
to ; we have learned perhaps all that we can learn about 
that cluster or stream ; but we can no more be said to have 
reached the limits of the sidereal system in that direction 
than we can be said to have reached the outermost bounds 
of the universe in the direction of the cluster in Hercules, 
when that magnificent object has been thoroughly re- 
solved with the telescope. 

Here, then, if I have seemed to narrow the limits of 
the sidereal system by bringing the star-myriads of the 
Milky Way, which had been regarded as many times fur- 
ther from us than the lucid stars, into direct association 
with these luminaries, I make amends by pointing out 
that in all probability the limits of the sidereal system 
lie far beyond the range of the most powerful telescopes 
man has yet constructed. In fact, there is here a some- 
what singular interchange of position between the new 
and the accepted theories. According to the views usu- 
ally accepted, the small stars in the Milky Way are really 
as large, on the average, as the lucid stars ; whereas, ac- 
cording to my views, they are relatively minute. But 
according to the acccepted theories, the scattered stars 
of very low magnitude in the extra -galactic heavens 



MINOR STARS. 279 

must be regarded as relatively minute, since it has 
been rendered certain, according to those theories, that 
the limits of the sidereal system are relatively close in 
this direction, and we cannot suppose these stars to lie 
beyond those limits (as they must do, if really large). 
Now, according to my views, there is nothing to prevent 
these minute stars from including among their number 
orbs as vast as Sirius, or many times vaster. Nay, even 
within the galactic zone itself there are stars to which my 
theory gives as noble proportions as the accepted views. 
For in the southern Coal-sack there are minute telescopic 
stars, as Sir John Herschel tells us, and these orbs, ac- 
cording to the accepted views, must be regarded as be- 
longing to the galactic circle, though inexplicably segre- 
gated from their fellows. According to the views I have 
been led to form, many of these telescopic stars must be 
regarded as suns lying far beyond the galactic spiral, or 
perhaps associated with outer whorls of this spiral which 
ho telescope made by man can ever reveal to us. 

And this leads me to consider two phenomena which 
are altogether inexplicable, I conceive, on any theory ex- 
cept mine. 

The first is the existence of excessively faint streams of 
light — star-streams, doubtless, though the components 
are not separately visible — in certain regions of the 
heavens. Sir John Herschel, who detected this strange 
phenomena, speaks of the streams as so very faint that 
the idea of illusion has continually arisen subsequently ; 



280 OTHER WORLDS THAN OURS. 

yet he dwells far too clearly on the charactistics of the 
phenomenon for any doubt to remain as to its reality. 
The faintest possible stippling of the field of view — the 
minute points of light being obviously there, though it 
was impossible to see them individually — a mottling 
which moved with the stars as he moved the tube to and 
fro, such are the terms in which Sir John Herschel speaks 
of this interesting phenomenon. 

Now no doubt whatever can exist that if these faint 
streams really belong to the sidereal system they are left 
altogether unaccounted for by the ordinary views respect- 
ing the structure of that system. There is no continuity 
between the stars composing them and even the minutest 
telescopic stars visible in the same general direction ; so 
that a vast void must separate them from the outermost 
of those telescopic stars. According to my theory, they 
probably belong to outlying whorls of the spiral galaxy, 
and the telescopic stars seen upon them bear the same re- 
lation to them that the lucid stars bear to the Milky Way. 

The second point is perhaps even more striking. In 
certain directions Sir John Herschel recognized the exist- 
ence of two or more distinctly marked classes of stars, as 
though, he said, definite sets of stars, separated by com- 
paratively void intervals, lay in those directions. It is 
clear that this association of the stars into sets is as dis- 
tinctly opposed to the views ordinarily accepted as it is 
obviously an arrangement to be expected according to my 
theory of the constitution of the sidereal system. 



MINOR STARS. 281 

But we need not proceed beyond the sphere of the lucid 
stars in order to find evidence of such association. Amaz- 
ing and incredible as it may at first sight appear, those 
orbs which have been visible during so many thousands of 
years before the telescope was invented, the stars which 
Hevelius and Ptolemy could chart and catalogue, have 
been teaching men with unmistakable clearness a lesson 
which hitherto has been persistently neglected. 

It had long since occurred to me that the lucid stars 
are not spread over the heavens with that general ap- 
proach to uniformity required by the accepted theories. 
In constructing my gnomonic charts of the heavens, 
though these include only the stars of the first five orders 
of magnitude, I recognized clear traces of the existence 
of star-streams and star-reticulations, rich regions and 
barren spaces, which the laws of probability would not 
permit me to regard as due to chance-distribution.* 

* I tried the experiment of distributing 2,000 points at random over 
a square surface. It is not quite so easy as it might at first be thought 
to secure a perfectly random distribution. The plan I adopted was the 
following : Taking a book full of numerals (I used a table of loga- 
rithms), and opening it at random, I brought the point of a pencil down 
on the open page. AVhatever numeral the pencil-point fell nearest to, 
I entered in a long list of numerals formed on this plan. Then divid- 
ing the sides of my square into 100 parts, and the square itself into 
10,000 small squares, I took the numerals in sets of four to indicate 
the places of a number of dots. Thus, supposing the first four numer- 
als to be 2371, I took that small square which was the twenty-third 
from one side of the large square and the seventy-first from an adjacent 
side, and marked a dot in that square. Doing this for 2,000 dots I bad 
a perfectly random distribution. No well-marked streams, reticula- 
tions, vacuities, or rich regions could be recognized in the result. I 



282 OTHER WORLDS THAN OURS. 

But while my larger atlas was in progress this opinion 
grew into conviction. In some of the maps the bareness 
of certain regions contrasted so strangely with the rich- 
ness of others as to give an unfinished appearance to the 
work. I determined that as soon as I had leisure I 
would combine in two large maps of hemispheres the 
twelve maps of my atlas, in order to see what the real re- 
lations might be which were only partially indicated in 
maps covering but a tenth part of the heavens.* I se- 
lected for this purpose a mode of projection described in 
my " Handbook of the Stars," but first suggested, I have 
since found, by Sir John Herschel. It represents equal 
areas on the celestial sphere by equal areas in piano ; so 
that, though there is considerable distortion, the real rel- 
ative richness of different regions of the stellar heavens 
is accurately represented. The accompanying large plate 
(Fig. 9) represents a reduction of the maps thus con- 
structed. 

I leave the exhibition of minor peculiarities of stellar 
distribution — star-streams, star-reticulations, star-clus- 
ters, and so on — to the maps themselves, which will, I 
think, be found to well repay careful study. But I ap- 
plied to the original maps a further process of investiga- 

eonsider, too, that where so many dots were marked in, one trial was as 
good as a large number. 

* The maps of my atlas overlap each of the twelve, including a tenth 
part of the celestial sphere. The reader may perhaps be surprised 
that the peculiarities I refer to should not have been noticed while 
other star atlases were constructed. But the great distortion in all 
former star atlases will suffice to explain the circumstance. 



MINOR STABS. 283 

tion in order to deduce the real characteristics of the 
rich and barren regions I had noticed while constructing 
the large atlas. The plan I adopted was sufficiently sim- 
ple. I cut out the portions of the map which seemed 
richly or sparsely dotted with stars and weighed the pa- 
per. The relative weights of different portions gave me 
the relative areas, and thus it was only necessary to 
count the number of stars in order to determine the rela- 
tive richness of stellar distribution. 

The regions I selected for special examination by this 
method were the following : 

1. A nearly circular region in the northern heavens 
surrounding the projection of the Milky Way toward the 
North Pole, and having a radius of about one-fifth of the 
map's diameter. I call this the richest northern region. 

2. A much larger region, including the last, and occupy- 
ing the middle of the northern map. I call this the rich 
central northern region. 

3. A large circular region, occupying the middle of the 
southern map. I call this the rich central southern region, 

4. A somewhat triangular region, included within the 
last, and occupying the upper right-hand part of the 
southern map (between Sirius, Canopus, and the constel- 
lation Crux). I call this the richest southern region. 

5-6. The remaining, or outer, parts of the northern and 
southern maps. 

7-8. Two very barren regions bordering on the rich 
northern central region — one toward the lower half of the 



284 



OTHER WORLDS THAN OURS. 



northern map, the other toward the upper half. I call 
these the poorer northern regions I. and II. 

9-10. Two corresponding southern regions, one occupy- 
ing the upper right-hand quadrant of the northern map, 
the other occupying the lower quadrant of the same side. 
These I call the poorer southern regions I. and II. 

Lastly, I take the northern and southern portions of the 
Milky Way, and the gaps and lacunae in the Milky Way. 

Having selected these regions for comparison,* and ap- 
plied to them separately " the scissors and balance " test, 
I have deduced the following results : 



Name of Begion. 



Northern — 

Milky Way 

Richest region 

Rich central region. 

Outer region 

Poor region (I.) 
Poor region (II.) . . . 

Gaps in Milky Way. . . 

Southern — 

Poor region (I.) 

Poor region (II.). . . . 

Outer region 

Rich central region. 

Richest region 

Milky Way 

Milky Way as a whole 



Area (Area of 
Hemisphere, as 1). 



A 

A 

A 
A 
A 
A 



A 
* 
* 

A 
A 



aVffths of sphere 



Number 

of Lucid 

Stars. 



497 
622 
1,420 
1,070 
201 
175 

20 



181 

216 
893 

2,467 
895 
618 



Richness 

(Average = 

5,850). 



9,940 
9,050 

6,248 
3,923 
2,948 
2,567 

1,240 



2,361 
3,198 
3,572 
9,868 
13,126 
13,596 



11,681 



* There is some room for choice in taking the boundaries of the 
regions, and for convenience I have so taken them that the smaller 
regions are made equal to each other in area. 



MINOR STABS. 285 

But surprising as these results may seem, the question 
whether such peculiarities of stellar arrangement may 
not be regarded as due to chance-distribution remains to 
be considered. 

It has been so often urged that among a very large 
number of stars such peculiarities might be looked for 
that many will be disposed to dispute the assertion that 
uniformity, not peculiarity of distribution, is to be ex- 
pected among a large number of points spread over any 
surface according to true chance-distribution. Yet so it 
is. The laws of probability tell us that whereas among a 
few such points peculiarities need not surprise us, uni- 
formity of distribution will inevitably appear where there 
are many points, unless some special law is in operation 
to prevent such a result.* 

To illustrate the amazing weight of probability in favor 
of the existence of laws of aggregation and segregation 
among the lucid stars, I will state the result of a process 
of calculation I have applied (in accordance with the 
recognized laws for determining probabilities) to the 



* As a familiar illustration of the law of probabilities in question, we 
may take the case of tossing a coin. If a coin be tossed six times, there 
will be nothing very surprising in the recurrence of " head " (say) four, 
five, or even six times— that is, if two thirds, five sixths, or the whole 
of the series of results are of one kind. But if we calculate the chance 
that in six thousand tossings there should be so many as four thousand 
results of one kind, we find it so minute that the concurrent testimony 
of all mankind could never make it credible that such an event had 
happened. The probability is the same as that referred to in the text 
a few lines further on. 



286 OTHER WORLDS THAN OURS. 

statistical relations presented by the two rich regions in 
the northern and southern hemispheres : 

The vast scale of the universe of the nebulse (or, as it 
has been called, the universe of universes), as conceived 
by Sir W. Herschel, is well known. Now, the probability 
that tlie observed relation results from chance-distribution 
is many millions of times less than the chance of drawing 
one particular grain, smaller many million-fold than the 
minutest object visible in the 'most powerful microscope and 
lying ivithin a space compactly filled with similar grains, 
and large enough to inclose many millions of the universes 
of universes. 

The probability that the more remarkable relations pre- 
sented by the richest and poorest smaller regions result 
from chance-distribution is indefinitely more minute even 
than this inconceivably minute probability. 

But since the above lines were written I have gone 
much further with the illustration of this matter by star- 
charting. For I have combined in a single chart all the 
forty large folio charts of Argelander's Atlas, containing 
no less than 324,198 stars, all presented on the same iso- 
graphic projection as the chart shown in Fig. 9. In this 
map of many stars, the place of the Milky Way is actually 
" mapped in " by the stars themselves, not as here, by a 
separate indication. I would refer those who desire fuller 
information respecting the arrangements of the stars in 
space to this chart and its explanation (published by Mr. 
Brothers, of 14 St. Ann Square, Manchester). 



MINOR STABS. 287 

The evidence in favor of special laws of stellar distribu- 
tion is, however, far from exhausted.* 

Quite early in my consideration of the subject I am 
now upon, the idea suggested itself to me that in the 
proper motions of the stars we have a means of forming 
an estimate of the distances of these orbs ; and further, of 
detecting any laws associating them together, whether 
into streams or clusters; and that the evidence thus ob- 
tained was likely to be in many respects more trustworthy 
than that afforded by the apparent magnitudes of the 
stars. Two processes of inquiry suggested themselves. 
The first consisted in a careful comparison of the mean 
motions of stars of different apparent size, in order to de- 
termine whether, on the average, small stars are so far off 
that we can look upon them as in reality no smaller on 
the average than those which appear larger. The second 
consisted in charting down the proper motions, so as to 
detect any signs of star-drift which might haply appear 
in different parts of the heavens. I confess that I had 
not by any means expected results so strikingly confirma- 
tory of my views as those I actually obtained. 

The first method of inquiry, instead of giving an aver- 
age amount of proper motion to the smaller stars some- 
what, or perhaps even considerably, greater than was to 
be expected, according to the theory which sets these 

* Indeed, I am unable, within the space here available to me, even 
to touch on a tenth part of the evidence I have gathered together in 
my note-books and portfolio of charts. 



288 OTHER WORLDS THAN OURS. 

stars at an enormous distance, actually gave them a mean 
motion equal to that of stars of the first three magni- 
tudes. It became evident, then, that not only are small 
stars (I am here speaking of stars visible to the naked 
eye) mixed up as I had thought with bright stars visible 
in the same general direction, but that distance is less 
available to explain the smallness of the stars even than I 
had supposed. I had thought that certainly a large pro- 
portion of the small stars must in reality be very far from 
us; but it appeared that the proportion of stars whose 
smallness is so to be accounted for is in reality exceed- 
ingly minute. There must therefore be myriads of really 
small stars for every leading orb. 

The second method of research led to the strange re- 
sult that in many parts of the heavens a community of 
motion can be recognized, among star-groups far larger 
in extent than any such groups as I had expected to find 
thus drifting through space. Knowing that whatever 
view we form of the sidereal universe, we must yet recog- 
nize the fact that in every direction stars at different dis- 
tances are visible, I had not hoped to find over any large 
region of space the traces of a community of motion. 
Nor even in small regions had I hoped to recognize very 
decided traces of star-drift, because I was conscious that, 
even with three or four stars really forming a drifting 
group, there would nearly always be found three or four 
others, either much further off or much nearer, and alto j 
gether dissociated from the drifting set. Indeed, I 



MINOR 8TAUS. 289 

imagined, when I began the inquiry, that the most re- 
markable instance of star-drift in the heavens was that 
detected (though differently explained) by Madler in the 
constellation Taurus. 



-it 







/ 

Fig. 10.— Drift of the Stars in the Constellations Cancer and Gemini. 

I found, however, that in other regions a far more ob- 
vious tendency to drift can be recognized. Perhaps the 

most remarkable instance of all is that illustrated in the 
19 



290 OTHER WOBLDS TRAN OUUB. 

plate (Fig. 10). This picture represents the motions in 
the constellations Cancer and Gemini. It will be noticed 
that though here and there stars apparently not belonging 
to the system appear in the same range of view, yet the 
star-drift is unmistakable. The general parallelism of mo- 
tion is very striking ; and the difference in the amount of 






=- - — ai*Zs' i 



/ 



y 



Fig. 11.— Obseeved Proper Motions of Stars in Ursa Major and Neighbor- 
hood. 

motion observed indifferent stars is only what was to 
be expected in a star-group whose range in distance, if 
equivalent to its lateral extent, must be such as fully to 
account for the range in the amount of apparent motion. 

Fig. 11 exhibits one out of the many parts of the heavens 
in which different sets of stars are observed to be drifting 
in different ways. 



MINOR STARS. 291 

It will be seen that here there are three sets — those in- 
cluded in the space a, those in space b, and those left un- 
inclosed. These groups are very obviously drifting, each 
in its special direction. The stars within the space b are 
ft, y, 8, e, and £of the Greater Bear with three smaller stars. 
Their drift is, I think, most significant. If in truth the 
parallelism and equality of motion are to be regarded as 
accidental, the coincidence is one of a most remarkable 
character. But such an interpretation can no longer be 
looked upon as admissible. For 
Mr. Huggins has found that these m 

stars (3, 7, 8, e, and f are all reced- j£ ~ 

ing from the earth at the rate of "^ ♦' 

about seventeen miles per second. ^ 1 m y 

This was the one piece of evidence f v 

necessary to establish my theory, Fm> 12 ._ 0bser ^ d Propeb 
that these stars form a drifting motions of stars in head 

of Aries. 

system. But the peculiarity is only 

one of a series of instances, some of which are scarcely 
less striking. One of these is presented in Fig. 12, in 
which the proper motions in the stars a, /3 and 7 Ari^ 
etis, and four other stars in the neighborhood, are ex- 
hibited.* 

Here /? and 7 may be regarded as drifting with a, but 
having a motion of their own in addition, sufficing to 

* In all three figures the proper motion indicated by the length of the 
arrow attached to a star corresponds to the star's motion in 36,00© 
years. 



292 OTHER WORLDS THAN OURS. 

account for the want of strict parallelism between tkeir 
apparent motion and that of a. The other stars seem 
obviously to belong to the same system. 

I am led by the facts which have here been briefly con- 
sidered rather to urge those who have time and inclina- 
tion to inquire carefully into the minuter details of the 
sidereal heavens than to insist on any views of my own. 
While I recognize the wisdom and necessity of that 
course which the Herschels adopted in taking a wide view 
of the sidereal system, and in dealing rather with general 
results than with special peculiarities, I think the time 
has come when another course is possible and advisable. 
The Herschels having surveyed the field of heaven, it be- 
hooves us now to go over it with a close and searching 
scrutiny. To consider averages now is to level the 
scarcely perceptible undulations in our field of research, 
as well as its better marked ridges or depressions; 
whereas we require, on the contrary, to exaggerate the 
variations of level, so that we may determine with more 
certainty what are the peculiarities presented by that 
most interesting field to man's contemplation. Or, to 
change the illustration, and to quote the words of the 
greatest modern master of that kind of research which I 
have been advocating, " We must not be deterred from 
dwelling consecutively and closely on these speculative 
views by any idea of their hopelessness which the ob- 
jectors against ' paper astronomy ' may entertain, or by 
the real slenderness of the material threads out of which 



MINOR STARS. 293 

any connected theory of the universe has (at present) to be 
woven. ' Hypotheses Jingo ' * in this stage of our knowl- 
edge is quite as good a motto as -Newton's c Non Jingo, 
provided always they be not hypotheses as to modes of 
physical action for which experience gives no warrant." f 



* It should be noticed that Newton defined wliat he meant by " hy^ 
potheses" when he said " hypotheses non jingo," and that he did not 
object to what have now commonly (through the careless use of words) 
come to be regarded as hypotheses. Newton defined a hypothesis as 
whatever is not deduced from the phenomena. 

f From a letter addressed by Sir J. Herschel to the present writer^ 
August 1, 1869. 



294 OTHER WORLDS THAJT OURS. 

OHAPTEB XII. 

THE NEBULA : ARE THEY EXTERNAL GALAXIES ? 

In the last chapter I have indicated reasons for believ* 
ing that the sidereal system extends far beyond the range 
of the most powerful telescopes man has yet been able to 
construct. It need hardly be said that, supposing this 
view to be correct, we cannot possibly see any external 
galaxies unless they surpass our own many thousands of 
times in richness and splendor. Every analogy that we 
have for our guidance points to the conclusion that if our 
galaxy have limits, and there exist in space other galax- 
ies, then those outer systems must be separated from ours 
by spaces exceeding the dimensions of the several galax- 
ies many thousand or many million-fold in extent. "We 
know that the distances separating the satellites from 
their primaries exceed in an enormous ratio the dimen- 
sions of the satellites. The distances separating the 
planets from each other exceed in an enormous ratio the 
dimensions of the planets. The distances separating the 
solar system from others enormously exceed the dimen- 
sions of the various solar systems. And we may conclude 
that in all probability the distances separating our side- 
real system from other similar systems in space must 
exceed in an enormous ratio the dimensions of our gal- 
axy, and of all other such systems. 



THE NEBULA. 295 

That the sidereal system has limits I do not doubt. 
Of course it may be co-extensive with space — that is, ab- 
solutely infinite in extent. But we have no reason for 
believing that in rising step by step, from system to sys- 
tem, until we have reached the highest class of system 
known to us, we have reached the real summit of that 
perhaps altogether limitless range of steps. We know, 
indeed, that if light do not suffer extinction in traversing 
space (and we have as yet no evidence that it does), the 
extent of the sidereal system must be limited, since other- 
wise the whole of the star-lit sky should shine with the 
brilliancy of sunlight.* And we may carry this argu- 

* This is, perhaps, obvious ; but if not, the following proof may be 
accepted : Let the whole of space be conceived divided into spherical 
shells, having our earth at the centre, the thickness of each shell being 
t. Then taking two shells, one at a distance r, the other at a distance 
r' (both r and r much greater than t), we see that the number of stars 
in these shells will be proportional to r*r and r'*r respectively — that is, 
will vary as the product of the thickness of the shell and the square of 
its radius. (Herb I am not concerned with those departures from uni- 
formity which I have considered in the last chapter, because I suppose 
each shell large enough to include within it all varieties of distribution 
and aggregation. This applies also to what follows.) Now the aver- 
age apparent size of the stars of one shell will be to the average appar- 
ent, size of stars in the other in the inverse proportion of the respec- 
tive radii of the shells, the intrinsic brightness of the light received 
from the stars of each set being equal. Thus the total amount of light 
from the stars of one shell is to the total amount of light from stars in 
the other as 

1 1 

rV x — : r'*r x — = 1:1. 

1 

Hence, supposing the amount of light received from one shell to be — th 

k 

part of that which would be received if the whole celestial sphere 



296 OTHER WORLDS THAN OURS. 

ment even further. For, though the sidereal system 
should be limited, but other systems similar to it spread 
throughout the infinity of space, there would still result 
this ineffable blaze of Light, surpassing the light of day as 
greatly as the vault of heaven surpasses the disk of the 
sun. And this again would be true, though this system 
of systems were limited in extent, but surrounded by 
similar systems of systems in the infinity of space. And 
so on, let the order of systems which finally becomes in- 
finite in number be what it may. There is only one way 
to escape from this limitless series of system-orders — 
that is, by accepting as true the hypothesis that light 
suffers extinction as it voyages through space. But it is 
worth noticing, when we are actually dealing with the 
infinity of space, and when, therefore, limitless concep- 
tions are not paradoxical, but in reality as available for 
our purposes as finite conceptions would be, that if we do 
adopt the belief in an infinite succession of orders of sys- 

were as bright as the sun's (that is, as a star's) disk — k being enor- 

1 
mcmsly large, the amount received from the other is also — th of this 

k 
amount, and the total from all the shells must therefore be 

1111 
1 H 1 = infinity. 

fc fc fc fc 
Now, by taking k terms of this series (or k shells out of our infinite 
series of shells) we should get unity, that is, the whole heavens lighted 
up with starlight or sunlight. There would be a proportion of stars in 
the same visual line, and so hiding each other ; but since we can take 
2 k, 3 k, or infinity times k if need be, there can be no doubt that the 
whole heavens would be lighted up with solar brightness. Compare 
next note. 



THE NEBULA. 297 

terns ; that is, first satellite-systems, then planetary-sys- 
tems, then star-systems, then systems of star-systems, 
then systems of systems of star-systems, and so on to in- 
finity ; and if we accept as true of this infinite series what 
we know to be true of the part within our ken, viz., that 
the distance between the components forming any system 
is indefinitely great compared with the dimensions of 
these components, we no longer have as a conclusion 
that the whole heavens would be lighted up with stellar 
(that is, with solar) splendor ; even though, in this view 
of the subject, there are in reality an infinite number of 
stars, just as in the view according to which the sidereal 
system extends without interruption to infinity.* 

* It is clear that we no longer get, as in the previous note, a 
series of equal small terms. If we take our infinite series of shells as 

1 
before we get for the sidereal system n times — where n is finite, 

k 
n n 

and therefore — finite. We must indeed assume — to be small, and 

k k 

so of other similar ratios presently to be dealt with. With respect to 
the system of systems, we have these considerations to guide us : 
Any of the spherical shells within this system must supply to our 
skies an amount of light indefinitely less than one of the shells within 

1 
the sidereal system itself, say — th part only, k' indefinitely large. 

k' 

But the number of shells falling within that system is very much 

greater, say n times as great where n is finite. Therefore we get 

for the total amount of light coming from the system of systems a 

n 7i 

quantity proportional to . And so for the system of system of 

kk' 

n n' n" 

systems we get a quantity proportional to , where k" is indefi- 

kKk" 



298 OTHER WORLDS THAN OURS. 

But whether we adopt this or any other view of the way 
in which external systems are arranged, this at any rate is 
certain, that if the stars at the outer parts of our own 

nitely large, n" very large. And for each successive order we get 

N 
a multiplier of the form — , where K is indefinitely large, and n very 

K 
V 

large indeed. Suppose — to be the largest of all these multipliers, 

7T 

then the total amount of light received from the infinite system of sys- 
tems is proportional to less than 

v v 1 v 3 
1 H 1 1 = infinity 

k \ 7T 7T 2 7T 2 

(in which v is supposed to be less than tt), i.e. to less than 



k \ TT — V 

a finite quantity — which, will even be minute if k and t are severally 
much greater than n and v. 

This particular mode of escaping from the difficulty suggested by the 
illumination of the heavens, without adopting the theory that light 
suffers extinction in its passage through space, occurred to me while I 
was preparing a series of papers entitled " A New Theory of the Uni- 
verse," which appeared in the Student in the spring of 1869 ; and I 
there exhibit the considerations just dealt with.- I was much pleased to 
find from a letter of Sir John Herschel's that the same idea had (prob- 
ably earlier) suggested itself to him ; and I was thus encouraged to be- 
lieve that I had not gone very far astray in the whole series of papers, 
whereof the matter in question had seemed to me the most speculative 
portion. The following are the words in which Sir John Herschel ex- 
presses the ideas above dealt with : " One of the arguments advanced 
in favor of the spatial extinction of light was that, if there is not such 
extinction, the whole heavens ought to be one blaze of solar light — 
admitting the universe to be infinite — because it was contended that 
there could then be no direction in space in which the visual ray 
would not encounter a star (i.e. a sun). This argument is fallacious, 
for it is easy to imagine a constitution of a universe literally infinite 
which would allow of any amount of such directions of penetration as 
not to encounter a star. Granting that it consists of systems subdivided 



TEE NEBULA. 299 

sidereal system be beyond the ken of our most powerful 
instruments — and I have shown that there are strong 
reasons for this conclusion — then the component suns of 
external galaxies cannot by any possibility be visible. So 
that, according to this view, all resolvable nebulae, at least, 
must be dismissed from the category of external galaxies. 
Nor will it be thought probable that irresolvable nebulae 
are external galaxies, if once that view of the extent of 
the sidereal system is adopted. 

But there are independent considerations on which I 
prefer now to dwell, for believing that all the nebulae be- 
long to the sidereal system. 

It will hardly be necessary, let me remark in passing, 
for me to point out how this matter is associated with the 
subject of other worlds. It is true that when once it is 
admitted that there are external galaxies, it may be looked 
on as a matter of small importance (so far as the subject 
of this treatise is concerned) whether we can actually see 
those galaxies or not. I am not, for instance, in the same 
position as Dr. Whewell, who assigned to the nebulae what 

according to the law that every higher order of bodies in it should be 
immensely more distant from the centre than those of the next infe- 
rior order — this would happen. Thus in our own, the moon is very 
near the earth, the satellites to their primaries. These primaries are 
immensely more distant from the sun, their centre ; the fixed stars 
again still more immensely more remote from the sun. Suppose our 
system to terminate with the visible fixed stars ; then imagine a system 
of such systems as remote from each other, in comparison with their 01011 
dimensions, as the distance of the fixed stars in comparison with the 
planetary system ; such systems seen from each other would subtend no 
greater angle than a star seen from the sun— and so on." 



300 OTHER WORLDS THAN OURS. 

I take to be their true place in the universe, with 
the express object of overthrowing the belief that there 
exist other galaxies as vast as the sidereal, or vaster, 
thronged with suns which are severally the centres of 
planetary systems, within which again are worlds as well 
suited to be the abode of life as this earth on which we 
dwell. But, though my purpose is different from his, it 
is equally necessary that I should insist on the true posi- 
tion of the nebulae. Because, if these objects form in- 
deed parts of the sidereal system, the relations they pre- 
sent are of extreme importance. They exhibit to us with- 
in the bounds of our galaxy systems altogether different 
from the solar system, and thus suggest ideas of other 
classes of worlds peopled with their own peculiar forms 
of life, as distinct perchance even in their general charac- 
teristics from any found amid the systems circling round 
stars, as the forms of life in Yenus or in Mars must be 
in their special characteristics from those existing on 
our own earth. 

Freed from those analogies which led the elder Her- 
schel to regard the stellar nebulae — resolvable and irre- 
solvable * — as external star systems, let us consider the 
relations presented by these and other nebulae without 
reference to preconceived opinions. 



* By irresolvable stellar nebulae I mean those nebulas which, though 
not resolvable into stars, yet present the characteristic features which 
lead astronomers to believe that only increase of telescopic power is 
needed iu order to effect resolution. 



THE NEBULA. 301 

We must first pay attention to one of the most striking 
of the discoveries which the spectroscope has yet enabled 
man to make — the discovery that certain nebulae are 
gaseous. It is necessary to consider this significant dis- 
covery, rather than those which were the first to exhibit 
the real place of the nebulae in our scheme, because we 
shall thus be able to divide the nebulae at once into two 
great classes, instead of being led to this arrangement by 
following out the history of those long processes of re- 
search by which the two great orders of nebulae were long 
since separated from each other under the piercing scru- 
tiny of Sir William Herschel. 

The reader will see how the spectroscope could at once 
resolve a question which ordinary observations would be 
all but powerless to deal with. The nebulae being self- 
luminous, the nature of the matter which is the source of 
their light would be shown by the character of the spec- 
trum, as distinctly as though that matter were actually 
present in the laboratory of the spectroscopist. 

Mr. Huggins thus describes the observation which first 
revealed the true nature of certain orders of the nebulae. 
The object under examination was a nebula in Draco, be- 
longing to the class of planetary nebulae : "On August 
19, 1864, I directed the telescope armed with the spec- 
trum apparatus to this nebula. At first I suspected some 
derangement of the instrument had taken place, for no 
spectrum was seen, but only a short line of light perpen- 
dicular to the direction of dispersion (that is, to what 



302 OTHER WORLDS THAN OURS. 

would in the case of solar light be the length of the spec- 
trum). I then found that the light of this nebula, unlike 
any other extra-terrestrial light which had yet been sub- 
jected by me to prismatic analysis, was not composed of 
light of different refrangibilities, and therefore could not 
form a spectrum. A great part of the light from this nebu- 
la is monochromatic, and after passing through the prisms 
remains concentrated in a bright line, occupying the posi- 
tion of that part of the spectrum to which its light corre- 
sponds in refrangibility. A more careful examination, 
however, showed that — a little more refrangible than the 
bright line, and separated from it by a dark interval — a 
narrower and much fainter line occurs. Beyond this, 
again, at about three times the distance of the second 
line, a third exceedingly faint line was seen. The posi- 
tions of these lines in the spectrum were determined by 
a simultaneous comparison of them in the instrument, 
with the spectrum of the induction spark taken between 
electrodes of magnetism. The strongest line coincides in 
position with the brightest of the air-lines. This line is 
due to nitrogen. . . . The faintest of the lines of 
the nebula agrees in position with a line of hydrogen." 
The other bright line was not found to correspond with a 
known line of any terrestrial element. Besides the bright 
lines, an exceedingly faint spectrum was just perceived 
for a short distance on both sides of the group of bright 
lines. Mr. Huggins suspected that this was not uniform, 
but crossed by dark places. Subsequent observations on 



THE NEBULA. 303 

other nebulae * induced him "to regard this faint spec- 
trum as due to the solid or liquid matter of the nucleus, 
and as quite distinct from the bright lines into which 
nearly the whole of the bright light from the nebula is 
concentrated." 

Thus was solved a problem which had, for the best part 
of a century, perplexed astronomers. There was not, in- 
deed, a full answer to all the questions of interest associ- 
ated with the problem. But it had been laid down by 
Sir William Herschel, as a legitimate conclusion from ob- 
servation, that certain orders of the nebulae are gaseous, 
and astronomers had ranged themselves for and against 
this proposition. Telescopic improvements had seemed 
at length to turn the scale in favor of those who held Sir 
William Herschel to have been mistaken. Already the 
problem had seemed all but definitely settled. And then 
in a moment this observation by Mr, Huggins had re- 

* One of the most interesting of Mr. Huggins' researches into the sub- 
ject of the light of nebulae is his attempt to determine its intrinsic 
brilliancy. By comparing the light of certain gaseous nebulae with 
that of a sperm candle (of the size called " six to the pound "), he 
found that these objects, assumed to be continuous, shine with a light 
varying in intrinsic brilliancy from the 1,500th to the 20,000th of that 
of such a candle. By a strange misconception, Mr. Lockyer, in discuss- 
ing Mr. Huggins' result, speaks of the comparison as though it related 
to the absolute brightness of the nebulae, saying that " such a candle a 
quarter of a mile off is 20,000 times more brilliant than the nebula." 
Mr. Huggins' result is wholly distinct from this, and much more im- 
portant. His comparison relates to the intrinsic luminosity of the neb- 
ular substance, not to the quantity of light received from the nebulae. 
(The distance of the candle in Mr. Huggins' observations is not con.« 
sidered in the result ; it was a mere matter of convenience.) 



304 OTHER WORLDS THAN OURS. 

versed the whole matter. It was now established beyond 
all possibility of future question that on the main point 
the greatest of modern astronomers had been altogether 
in the right. 

The orders of nebulae which give a spectrum of bright 
lines would seem from Mr. Huggins' observations to be 
(1) the planetary nebulae, (2) the ring nebulae, (3) the 
irregular nebulae. The spiral nebulae seem, for the most 
part, to give a continuous spectrum, but some of these 
objects give the bright-line spectrum indicative of gaseity. 
The orders of nebulae which give a continuous spectrum 
appear to be the following : (1) star groups, (2) clusters, 
regular and irregular, and (3) easily resolvable nebulae. 
Of the irresolvable nebulae a large proportion seem to be 
gaseous.* 

Here, then, we find the nebulae ranged into two im- 
portant divisions, apparently separated by a distinct line 



* The following classification of nebulae in this respect, by Lord 

Oxmantown, is interesting as indicating the results of observations 

made with so powerful an instrument as the great Parsonstown telescope 

(the 6-foot reflector) : 

Continuous Gaseous 
Spectrum. Spectrum. 

Clusters.... 10 

Certainly or probably resolved 5 

Certainly or probably resolvable 10 6 

Blue, or green, no resolvability 4 

No resolvability detected 6 5 

Total observed 31 15 

Adding nebulae not observed at Parsonstown, there are in all 41 which 
exhibited a continuous spectrum, and 19 which gave a spectrum indica- 
tive of gaseity. 



THE NmVLJS. 305 

of demarcation. Yet one is tempted to inquire whether 
these divisions may not in reality run into each other by 
the fact that among nebulae of certain orders are objects 
belonging to both divisions. And the fact that beneath 
the bright-line spectrum of the gaseous nebulae a faint 
continuous spectrum may be seen seems also to point in 
the same direction. We know that, so far as the tele- 
scopic appearance of the nebulae is concerned, there is 
very striking evidence of a gradual progression from 
clusters to irresolvable nebulae ; and therefore we are led 
to inquire whether the spectroscope conveys a similar 
lesson. 

Now this question could only be answered satisfactorily 
by the observation of a series of nebulae having spectra 
progressively varying, from bright lines on an almost in- 
visible continuous spectrum to a continuous spectrum 
with the same bright lines superposed on it, but almost 
imperceptible, because their brightness so little exceeded 
that of the continuous spectrum. We have no evidence 
of such completeness. But Captain Herschel has ob- 
served in the southern heavens a clustering nebula with a 
continuous spectrum, on which he could just detect the 
three bright lines seen in the spectra of the gaseous neb- 
ulae. So far as this evidence extends, the conclusion is 
obvious that the various orders of nebulae are orders of 
but a single family. It will be seen presently that this 
conclusion, which is strikingly corroborated by other evi- 
dence, has a very important bearing on the views we are 
20 



306 OTHER WORLDS THAN OURS. 

to form respecting the relations between the nebulae and 
the sidereal system. 

The first process by which we must attempt to form a 
correct estimate of the nebular system corresponds to Sir 
William Herschel's process of star-gauging. We must in- 
quire according to what general laws the nebulae are 
spread over the vault of heaven. 

Now, when this is done, it appears that there is a well- 
marked peculiarity in the arrangement of the nebulas, a 
peculiarity as striking as the existence of the galactic 
circle itself. Hie nebulm seem to withdraw themselves 
from the neighborhood of the galaxy. In the northern 
heavens they cluster very definitely toward the pole of 
the galaxy ; in the southern they are arranged in streams 
and clustering aggregations, but the galaxy itself is, in 
either case, left almost clear of nebulae. 

If this peculiarity is accidental, the coincidence in- 
volved is most remarkable. Had there been a zone of 
nebulae, and that zone had shown a tendency to coinci- 
dence with the Milky Way, the relation would have been 
thought strikingly indicative of a real association between 
the nebular and the sidereal systems. But is the direct 
converse of this relation more likely to be the effect of 
chance? Have not observers and experimenters con- 
cluded (in every other similar instance) that a law of con- 
trast is as indicative of a real connection as a law of as- 
sociation? Is it not most surprising, therefore, that 
nearly all astronomers who have considered the relation 



THE NEBULJB. 30? 

in question have regarded it as affording strong evidence 
that the nebular system is wholly dissociated from the 
sidereal ? 

Next let us turn to special features. In the first place, 
let us inquire whether the different orders of nebulae ex- 
hibit any peculiarities of arrangement. 

We find that clusters exhibit a very marked preference 
for the neighborhood of the Milky "Way ; resolvable neb- 
ulae seem to prefer the galactic zone, but not in so de- 
cided a manner ; and it is only among the irresolvable 
nebulae that we recognize that withdrawal from the Milky 
Way which had seemed characteristic of the whole neb- 
ular system before we considered its several orders. The 
fact that the irresolvable nebulae form about four-fifths of 
the total number will account for the circumstance that a 
peculiarity really appertaining to that order alone should 
appear to belong to the whole system of nebulae. 

Again, the planetary and irregular nebulae are found to 
affect the neighborhood of the Milky Way. I have already 
mentioned that these objects are gaseous. 

It is easy to see what general conclusions may be de- 
duced from the peculiarities here touched upon. Obvi- 
ously the first shows us most distinctly that there is a 
relation between propinquity to the Milky Way and the 
character of nebulae as respects resolvability — a relation 
which points in the most decisive manner to the existence 
of a close association between the sidereal system of which 
the Milky Way certainly forms part, and the nebular sys- 



308 OTBER WORLDS THAN OURS. 

tern from which clusters and resolvable nebulae cannot 
reasonably be separated. It is equally obvious that the 
second peculiarity indicates the existence of a close asso- 
ciation between the Milky Way and the character of the 
nebulas as respects gaseity ; a relation which brings all 
the gaseous nebulae into close association with the sidereal 
system, since we know that among the extra-galactic neb- 
ulae there are many which are principally formed of the 
very same gases which appear in the irregular and plane- 
tary nebulae. When we consider that those peculiarities 
of configuration and of constitution which have alike 
seemed to indicate that the various orders of nebulae 
merge into each other by indefinable gradations are both 
associated in a very distinct manner with the most marked 
peculiarity of the sidereal system, and when to this we 
add what has been already suggested by the relation of 
contrast between the irresolvable nebulae and the Milky 
Way, the conclusion seems forcibly impressed upon us 
that the nebular and the sidereal systems are but differ- 
ent parts of one single scheme. 

But I pass on to other evidence, independent of what 
has hitherto been adduced, and pointing with equal force 
to the same conclusion. 

In the northern heavens it is not very easy to exhibit 
any general law of arrangement associating the nebulae 
and the fixed stars. For reasons which yet remain to be 
detected, there are in fact many marked points of differ- 
ence between the whole character of the heavens on the 



TEE NEBULJ&. 30% 

northern and on the southern side of the galactic zone. 
But even in the northern heavens one peculiarity has been 
remarked, which is well worthy of careful consideration. 
Sir William Herschel, while prosecuting his series of re- 
searches among stars and nebulae, was struck by the cir- 
cumstance that, after sweeping over a part of the heavens 
which was unusually barren, he commonly met with nebu- 
las ; insomuch that it was his practice at such times to call 
to his assistant (his sister, Miss Caroline Herschel) to 
"prepare for nebulae." This peculiarity was noticed also 
by Sir John Herschel. 

Now what are we to understand by such a relation as 
this ? Can we suppose that, owing to some strange acci- 
dent, external galaxies have been placed always opposite 
the barest regions of the sidereal system? Or, setting 
aside such a notion as obviously incredible, are we to im- 
agine that when searching over those barren regions the 
astronomer has a better chance of detecting nebulae than 
where stars are more richly strewn, because the sky is less 
filled with glare ? We are forced to dismiss this notion 
that the barren regions of the heavens are thus in a man- 
ner the spy-holes of the sidereal system, by the fact (pres- 
ently, and for another purpose, to be dwelt on more at 
length) that in the Magellanic Clouds, where stars of all 
magnitudes are richly strewn, nebulae, even down to the 
very faintest orders, are more abundant than in any other 
region of the heavens. We have then no other conclusion 
to form, but that the association thus observed between 



310 OTHER WORLDS THAtf OURS. 

starless regions and richness of nebular distribution indi- 
cates a very close relation indeed between stars and nebu- 
lae ; that, in fact, the nebulce in a sense represent the missing 
stars ; that the region where those nebulce appear has been 
drained of star materials, so to speak, in order to form 
them. 

In the southern heavens yet clearer proofs exist of an 
association between the stellar and nebular systems. 
We do not recognize in the northern skies any well- 
marked star-streams. In the southern skies, however, 
such streams have been recognized from the earliest 
ages. The constellations Hydra and Eridanus, the two 
streams from the Water-Can of Aquarius, and the band 
between the Two Fishes,* indicate how clearly the an- 
cients traced certain well-marked star-streams. The 
moderns have traced the extension of some of these 
streams in the constellations Grus, Hydra, Eeticulum, 
etc., into the near neighborhood of the southern pole. 
Now the nebulae in the southern heavens exhibit a well- 
marked tendency to aggregate into streams. So that, in 
this mere resemblance between the general characteris- 
tics of the stellar and nebular systems in the southern 
heavens, we have a somewhat remarkable evidence of 
association. But when we consider the disposition of 
the two sets of streams — the stellar and the nebular — - 

* Though Pisces is not a southern constellation, yet it is south of the 
galactio circle, to which I am for the moment referring the constella- 
tions. 



THE NEBULA. 311 

this evidence is very much strengthened. There is found 
to be a well-marked correspondence between the nebular 
and stellar streams, not merely as respects general posi- 
tion, but even in minute details — the nebular streams fol- 
lowing the windings of the stellar ones. Such a relation 
would be very remarkable, even were it observed but in 
a single instance. Since, however, all the well-marked 
star-streams in the southern heavens are associated with 
well-marked nebular streams, no doubt can remain that 
the relation is not a mere coincidence, but indicates a 
real association between the nebular and stellar systems. 

But yet more striking evidence remains to be consid- 
ered. 

In the southern heavens there are two strange clouds 
of milky light, which have long been known by sailors 
as the Magellanic Clouds, but are commonly called by 
astronomers the Nubecula?. Each of these objects, when 
examined with the telescope, is found to be constituted, 
like the Milky Way, of multitudes of small stars. But 
unlike the Milky Way, the Nubecula contain within 
their bounds many nebulae of all orders. In fact, each 
of the Nubecula? is at once a star-cluster and a cluster of 
nebula?. 

Now there can be no doubt whatever that the associa- 
tion here is not accidental, that we do not by some 
strange chance see a great star-cluster in the same direc- 
tion of a much more distant and much vaster cluster of 
external galaxies. Nor again can there be any doubt 



812 OTHER WORLDS THAN OURS. 

that the generally circular figure of each Nubecula indU 
cates a general approach to the spherical form in the case 
of each cluster. The probability that by some strange 
accident a cluster of cylindrical shape* might be so 
placed as to exhibit to us a circular figure is exceedingly 
small ; but the chance that two such clusters should be 
presented in so exceptional a manner may be regarded as 
evanescent. We are compelled, then, to believe that, 
within the limits of spheres so placed as to subtend a 
small angle to the eye, stars of all magnitudes between 
the seventh and the twelfth, inclusive, are mixed up with 
nebulae of all degrees of resolvability. " Taking the ap- 
parent semi-diameter of the Nubecula Major at three de- 
grees," says Sir John Herschel, "and regarding its solid 
form as, roughly speaking, spherical, its nearest and most 
remote parts differ in their distance from us by a little 
more than a tenth part of our distance from its centre." 
" It must therefore be taken as a demonstrated fact," he 
adds presently, " that stars of the sevenths and eighth 
magnitude and irresolvable nebulas may co-exist within 
limits of distance not differing in proportion more than 
as nine to ten." This demonstrated fact of Sir John 
Herschel's is the very fact to which I had been led by 
other considerations, the fact, namely, that the nebulae 
are not external galaxies, but intimately associated with 
the sidereal system, of which, in fact, they form part and 

* Or, more correctly, a cluster shaped like a long frustum of a gi- 
gantic cone. 



TEE NEBULA. 313 

parcel. Dr. Whewell, accepting Sir John Herschers 
reasoning as conclusive on the point, adopted the same 
view. And although Sir John Herschel himself, imme- 
diately after establishing this noteworthy conclusion, 
speaks respecting it in a tone of philosophic caution, it 
must not be forgotten that to his clear vision the associ- 
ation between nebulae and fixed stars had presented itself 
as a demonstrated fact, and that even in the latest edi- 
tions of his noble work on astronomy he has not altered 
the words in which he has spoken of that association. 

Lastly, and perhaps most strikingly, the association 
between stars and nebulae is indicated by the obvious 
connection between the figure of the irregular nebulae 
and the arrangement of the star-groups seen in the same 
field of view. There is not one of the irregular nebulae 
which does not exhibit this peculiarity in the most strik- 
ing manner. This may be asserted even of those nebulae 
with respect to which Sir John Herschel has remarked 
that the arrangement may be accidental. His own pict- 
ures seem to me to prove in the most convincing manner 
that no such explanation can be accepted. The mere 
aggregation of a large number of stars in the very heart 
of a nebula might be an accident. The fact, for in- 
stance, that the great irregular nebula surrounding the 
star Eta Argus agrees exactly in position with the great- 
est condensation of the wonderfully rich portion of the 
Milky Way on which that surprising variable lies, might 
be a mere coincidence, though in any case it would be a 



314 OTHER WORLDS THAN OURS. 

strange one. But when one examines the structure of 
this and similar nebulae, and finds that the stars are ar- 
ranged in a manner most obviously related to the ar- 
rangement of the nebular condensations (or folds as one 
may almost say), one cannot doubt that a real and inti- 
mate bond of association exists between the stars and 
the nebulous masses around them. If the extension of 
the milky light of the great Orion nebula to the star i in 
the sword, which is centrally involved in strong nebulos- 
ity ; to e in the belt, which is similarly involved ; and to 
several other stars in the constellation (all alike in occu- 
pying regions of increased nebular condensation), be a 
mere accidental coincidence, then the laws of probability 
had better be forgotten as soon as possible ; for, as at pres- 
ent understood, they can only serve to lead men astray. 

In the accompanying plate (Fig. 13) is given a picture 
of the nebula Messier 17, as observed with Lassell's four- 
foot reflector at Malta. I have selected it as affording a 
very striking instance of the particular form of associa- 
tion I have just been dealing with. No one can, I think, 
refuse to recognize the fact that the system of stars 
shown in this drawing is not accidentally seen projected 
on a distant galaxy, but forms part and parcel of the 
nebula itself.* 



* Sir John Herschel, referring to the accompanying plate, expressed 
the opinion that the apparent association need not necessarily be real. 
The discovery of nebular tracts in the Pleiades has now practically 
demonstrated the validity of the opinion expressed in the text. 



THE NEBULA. 315 

The nebula around the strange variable star, Eta Ar- 
gus, already referred to, is another remarkable instance 
of this sort. More than two years ago I ventured to 
make two predictions about this object. The first was 
a tolerably safe one. I expressed my belief that the 
nebula would be found to be gaseous. After Mr. Hug- 
gins' discovery that the great Orion nebula is gaseous, it 
was not difficult to see that the Argo nebula must also be 
so. At any rate, this has been established by Captain 
Herschel's spectroscopic researches. The other predic- 
tion was more venturesome. Sir John Herschel, whose 
opinions on such points one would always prefer to 
share, had expressed his belief that the nebula lies far 
out in space beyond the stars seen in the same field of 
view. I ventured to express the opinion that those stars 
are involved in the nebula. Lately there came news 
from Australia that Mr. Le Sueur, with the great re- 
flector erected at Melbourne, has found that the nebula 
has changed largely in shape since Sir John Herschel 
observed it. Mr. Le Sueur accordingly expressed his 
belief that the nebula lies nearer to us than the fixed 
stars seen in the same field of view. More lately, how- 
ever, he has found that the star Eta Argus is shining 
with the light of glowing hydrogen, and he expresses 
his belief that the star has consumed the nebulous mat- 
ter near it. "Without agreeing with this view,* I recog- 



* My belief is that as the star recovers its brilliancy observation will 
show that the nebula in its immediate neighborhood becomes brighter 



316 OTHER WORLDS THAN OURS. 

nize in it a proof that Mr. Le Sueur now considers the 
nebula to be really associated with the stars around it. 

Among other instances may be cited the nebula round 
the stars c 1 and c 2 in Orion. In this object two remark- 
able nebulous nodules centrally surround two double 
stars. Admitting the association here to be real (and no 
other explanation can reasonably be admitted), we are 
led to interesting conclusions respecting the whole of 
that wonderful nebulous region which sin-rounds the 
sword of Orion. We become certain that the other 
nebulas in that region are really associated with the fixed 
stars there ; that it is not a mere coincidence, for in- 
stance, that the middle star in the belt of Orion is in- 
volved in nebula, or that the lowest star of the sword 
is similarly circumstanced. It is a legitimate inference 
from the evidence that all the nebulae in this region be- 
long to one great nebulous group, which extends its 
branches to these stars. As a mighty hand this nebu- 
lous region seems to gather the stars here into close as- 
sociation, showing us, in a way there is no misinterpret- 
ing, that these stars and the nebula form one system. 

It will be noticed, as respects the two proofs on which 
I have last dwelt, that they seem directly opposed to 
those which I first quoted. One cannot argue, it might 
be urged, that the nebulae are associated with the sidereal 

{not fainter through being consumed as fuel). In fact, I am disposed 
to regard the variations of the nebula as systematic, and due to orbital 
motions among its various portions around neighboring stars. 



THE KEBTJLJS. 317 

system because they are least numerous where there are 
most stars, and vice versa ; while at the same time one 
draws the same conclusion from the aggregation of the 
nebulae in streams or clusters where there are streams 
and clusters of stars, or from the fact that stars are seen 
actually mixed up with nebulous matter. At first sight 
this objection seems just ; but, on consideration, it will 
be found that, in reality, the two seemingly contrary 
lines of argument bear in the same direction. "When we 
find the nebulas gathered where stars are wanting, and 
vice versa, we conclude that there is some reason for 
this peculiarity, and that that reason must involve some 
sort of association between the nebulae and the stars ; we 
see, further, that the relation is accounted for if we sup- 
pose that, in these cases, either the formation of nebulae 
has drained a region of material from which single stars 
would otherwise have been formed, or vice versa. Why, 
in a particular region, the formation of nebulae should 
be encouraged, while the formation of stars should be 
checked, we cannot say ; nor can we account for the 
contrary peculiarity in another region : but we feel cer- 
tain that some cause must exist for both relations, be- 
cause the results are too marked to be due to accident. 
Now, in the case where we find both stars and nebulae 
abundant in particular parts of the heavens, we feel 
equally certain that the result is not accidental. Even 
though there were not here, as in the former case, the 
evidence of a clearing of star-material from certain re- 



318 OTHER WORLDS THAN OURS. 

gions, we could not doubt that the association of stars 
and nebulae was real, and not apparent. But in reality- 
there is here, precisely as in the former case, a gathering 
together of stellar matter into certain regions. The 
very existence of such a stream as Eridanus or Hydra, 
and of such a cluster as the greater or lesser Magellanic 
Cloud, implies the action of such a process of segrega- 
tion. A stream would not be recognizable if it were not 
bounded by relatively bare regions. Clusters like the 
Nubecula might be visible even on a rich sky — and were 
the sideral heavens richly strewn with stars round these 
objects I should be disposed to admit that there was a 
difficulty in my theory. But what is the fact? Not 
only is each of the Nubeculae placed in a region obvi- 
ously bare of lucid stars, but Sir John Herschel, speak- 
ing of the telescopic aspect of the neighborhood of these 
mysterious clusters, dwells again and again on its pov- 
erty. " A miserably poor and barren region," he says 
of one field near the Nubecula?. " The access to the Nu- 
becube," he says elsewhere, " is on all sides through a 
desert." What evidence could more clearly point to the 
fact that these great clusters are gathered out from a 
vast region of space ? Their internal structure teaches us 
how such a process of segregation leads to the birth of 
nebulae as well as stars. The whole history of the sidereal 
system is indeed taught us in the Magellanic Clouds and 
the great streams of intermixed stars and nebulae which 
How toward them as rivers toward some mighty lake. 



THE NEBULA. 319 

It remains that I should sum up the results which I 
have discussed in the last two chapters. It has seemed 
to many that my views tend largely to diminish our esti- 
mate of the extent of the sidereal system. The exact re- 
verse is the case. According to accepted views there lie 
within the range of our most powerful telescopes millions 
of millions of suns. According to mine the primary suns 
within the range of our telescopes must be counted by 
tens of thousands, or by hundreds of thousands at the 
outside. What does this diminution of numbers imply 
but that the space separating sun from sun is enormously 
greater than accepted theories would permit ? And this 
increase implies an enormous increase in the estimate we 
are to form of the vital energies of individual suns. For 
the vitality of a sun, if one may be permitted the ex- 
pression, is measured not merely by the amount of mat- 
ter over which it exercises control, but by the extent of 
space within which that matter is distributed. Take an 
orb a thousand times vaster than our sun, and spread over 
its surface an amount of matter exceeding a thousand-fold 
the combined mass of all the planets of the solar system : 
so far as living force is concerned, the result is nil. But 
distribute that matter throughout a vast space all round 
the orb ; that orb becomes at once fit to be the centre of 
a host of dependent worlds. Again, according to accept* 
ed theories, when the astronomer has succeeded in re- 
solving the milky light of a portion of the galaxy into 
stars, he has in that direction, at any rate, reached the 



320 OTHER WORLDS TB AiV~ OURS. 

limits of the sidereal system. According to my views> 
what he has really done has been but to analyze a defi* 
nite aggregation of stars, a mere corner of that great sys- 
tem. Yet once more, according to accepted views, thou* 
sands and thousands of galaxies, external to the sidereal 
system, can be seen with powerful telescopes. If I am 
right, the external star-systems lie far beyond the reach of 
the most powerful telescope man has yet been able to con- 
struct, insomuch that perchance the nearest of the out- 
lying galaxies may lie a million times beyond the range 
even of the mighty mirror of the great Kosse telescope. 

But this is little. Wonderful as is the extent of the 
sidereal system as thus viewed, even more wonderful is 
its infinite variety. We know how largely modern dis- 
coveries have increased our estimate of the complexity of 
the planetary system. Where the ancients recognized 
but a few planets, we now see, besides the planets, the 
families of satellites : we see the rings of Saturn, in 
which minute satellites must be as the sands on the sea- 
shore for multitude ; the wonderful zone of asteroids ; 
myriads on myriads of comets ; millions on millions of 
meteor systems, gathering more and more richly around 
the sun, until in its neighborhood they form the crown of 
glory which bursts into view when he is totally eclipsed. 
But wonderful as is the variety seen within the planetary 
system, the variety within the sidereal system is infinitely 
more amazing. Besides the single suns, there are groups 
and systems and streams of primary suns; there are 



THE NEBULA. 321 

vfhole galaxies of minor orbs ; there are clustering stellar 
aggregations, showing every variety of richness, of figure, 
and of distribution ; there are all the various forms of 
nebulae, resolvable and irresolvable, circular, elliptical, 
and spiral ; and lastly, there are irregular masses of 
luminous gas, clinging in fantastic convolutions around 
stars and star-systems. Nor is it unsafe to assert that 
other forms and varieties of structure will yet be discov- 
ered, or that hundreds more exist which we may never 
hope to recognize. 

But lastly, even more wonderful than the infinite vari- 
ety of the sidereal system is its amazing vitality. In- 
stead of millions of inert masses, we see the whole heav- 
ens instinct with energy— astir with busy life. The great 
masses of luminous vapor, though occupying countless 
millions of cubic miles of space, are moved by unknown 
forces like clouds before the summer breeze; star-mist 
is condensing into clusters ; star-clusters are forming into 
suns ; streams and clusters of minor orbs are swayed by 
unknown attractive energies ; and primary suns singly 
or in systems are pursuing their stately path through 
space, rejoicing as giants to run their course, extending 
on all sides the mighty arm of their attraction, gathering 
from ever new regions of space supplies of motive energy, 
to be transformed into the various forms of force — light 
and heat, and electricity — and distributed in lavish abun- 
dance to the worlds which circle round them. 

Truly may I say, in conclusion, that, whether we re* 
21 



822 OTHER WORLDS 1BAN OURS. 

gard its vast extent or its infinite variety, or the amazing 
vitality which pervades its every portion, the sidereal 
system is, of all the subjects man can study, the most 
imposing and the most stupendous. It is as a book full 
of mighty problems — of problems which are as yet al- 
most untouched by man, of problems which it might 
seem hopeless for him to attempt to solve. But those 
problems are given to him for solution ; and he will solve 
them whenever he dares attempt to decipher aright the 
records of that wondrous volume. 



SUPERVISION AND CONTROL. 323 



CHAPTEK Xm. 

SUPERVISION AND C0NTK0L. 

It is a peculiarity of the subject of other worlds than 
ours that it suggests more strikingly than any other cer- 
tain difficulties in connection with conceptions as to 
supervision and control exercised over the universe. 

Let us consider definitely (even though we must be un- 
able to conceive clearly or at all) the infinities we have to 
deal with. 

We know that space must be infinite. If the region 
amid which stars and nebulae are scattered in inconceiv» 
able profusion be limited, if beyond lies on all sides a 
vast void, or if, instead, there be material bounds inclos- 
ing the universe of worlds on every hand, yet where are 
the limits of void or bound ? Infinity of space, occupied 
or unoccupied, there must undoubtedly be. Of this in- 
finity it has been finely said that its centre is everywhere, 
its boundary nowhere. Now, whether within this infinity 
of space there be an infinity of matter is a question which 
we cannot so certainly answer. Only, if we were to ac- 
cept this as certain, that the proportion which unoccupied 
bears to occupied space cannot be infinitely great — a 
view which at least seems reasonable and probable — then 



324 OTHER WORLD? THAN OURS. 

it would follow that matter as well as space must be in- 
finite, since any finite proportion of infinity must itself 
also be infinite. 

Time also must undoubtedly be infinite. If the por- 
tion of time which has hitherto been, or which will here- 
after be, occupied with the occurrence of events (of what- 
ever sort) were preceded and will be followed by a vast 
void interval, yet there can be neither beginning nor end 
to either of those bounding voids. Infinity of time, oc- 
cupied or unoccupied, there must undoubtedly be. And 
though it is not possible for us to know certainly that 
there has been no beginning, or that there will be no end 
to that portion of time which is occupied with the occur- 
rence of events (of whatever sort), yet it appears so un- 
reasonable to conceive that unoccupied time bears an 
infinitely great proportion to occupied time that we seem 
led to the conclusion that occcupied time is infinite — or, 
more definitely, that there has been no beginning and will 
be no end to the sequence of events throughout the in- 
finitely extended universe. 

Now to conceive of limits to the wisdom and power of 
One whose realm is infinite in extent and in duration is 
obviously to conclude that the Euler is infinitely incom- 
petent to rule over His kingdom : for there can be no re- 
lation between the finite and the infinite save the relation 
of infinite disproportion. 

Senses such as we have we can no more attribute to 
such a Euler than we can assign to Him hands and feet. 



SUPERVISION AND CONTROL. 325 

Nor can we conceive in what way He can be cognizant of 
material processes which we only recognize through their 
material effects. Yet we can scarcely conceive of Him as 
other than cognizant of all those processes by which our 
senses can be affected. 

But before considering the nature of such a Being's 
supervision of His universe, we may proceed a step 
further. The senses we possess are sufficient to indicate 
to us the possible existence of senses not merely far more 
acute, but of a wholly different kind. By the sense of 
touch, for instance, we can indeed recognize the feeling of 
heat ; but it is easy to conceive of a sense (analogous to 
that by which light is made to teach us of the aspect of 
external objects) enabling men to judge of the figure, sub- 
stance, internal structure, and other qualities of an object 
by the action. of the heat-waves proceeding from it. Or 
again, electricity, instead either of light or of heat, might 
be the means of communicating intelligence as to the 
qualities of objects. We can conceive also of a sense 
bearing the same analogy to sight that the spectroscope 
bears to the telescope. And a hundred kinds of sense, 
or in other words, a hundred modes of receiving intelli- 
gence about what exists or is going on around us, might 
be readily conceived. 

Yet once more, we know that reason is able to range 
beyond the action of the senses. Man is able to assure 
himself that events have happened which yet have pro- 
duced no direct effect upon any of his senses. By the 



326 OTHER WORLDS THAN OURS. 

exercise of reason he becomes as well assured of such 
events as though they had actually passed before his 
eyes. An analogous power, but infinite in degree, infi- 
nitely rapid in its operation, and infinite in the extent of 
space and time over which it ranges, we may conceive to 
be possessed by a true Ruler over the universe. 

And now let us notice some of the conclusions to which 
these considerations tend. 

Let us first deal with the teachings of that sense which 
is the most far-reaching f of all the faculties given to man 
— the sense of sight. 

In a little treatise called " The Stars and the Earth," 
published anonymously several years since, some results 
of modern discoveries respecting light were dealt with in 
a very interesting manner. I propose to follow the path 
of thought indicated in that treatise, as a fitting introduc- 
tion to wider conceptions of supervision and control over 
the universe. 

We know from Romer's researches, and even more 
surely from the phenomenon termed the aberration of the 
fixed stars, that light does not travel with infinite velocity. 
Its speed is indeed so enormous that, compared with 



* Most persons, if asked which sense comes next to sight in this re- 
spect, would answer hearing. Yet touch — or rather feeling — has a range 
far exceeding that of hearing, since we can feel the heat emitted by 
the sun. Nor is it difficult to conceive of such an increase in the deli- 
cacy of the sense of touch that even the minute amount of heat received 
from the fixed stars might be felt, and so the range of the sense ex< 
tended many million- fold. 



SUPERVISION AND CONTROL. 327 

every form of motion with which we are familiar, the 
velocity of light appears infinitely great. In a single 
second light traverses a space equal to eight times the 
circumference of the earth; and therefore in travelling 
from any visible object on the earth to the eye of a ter- 
restrial observer, light occupies a space of time indefi- 
nitely short. Yet even as regards such objects as these 
light has occupied a real interval of time, however mi- 
nute, in reaching the eye ; insomuch that we see ob- 
jects not as they are at the moment we perceive them, 
but as they were the minutest fraction of a second be- 
fore. 

Raising our eyes from the earth to regard the celestial 
objects, we find, in place of the indefinitely minute inter- 
val before considered, a really appreciable space of time 
occupied by light in carrying to us information as to the 
condition of those distant orbs. From the moon light 
takes little more than a second and a quarter in reaching 
us ; so that we obtain sufficiently early information of the 
condition of our satellite. But light occupies more than 
eight minutes in reaching us from the sun ; a longer or 
shorter interval in travelling to us from Mercury, Yenus, 
and Mars, according to the position of these planets ; from 
about thirty-five to about fifty minutes in reaching ns 
from Jupiter ; about an hour and twenty minutes on th6 
average in speeding across the great gap which separates 
us from Saturn ; while we receive intelligence from Uranus 
and Neptune only after intervals respectively twice and 



328 OTHER WORLDS THAN OURS. 

three times as great as that which light takes in reaching 
us from the ringed planet. 

Thus, if we could at any instant view the whole range 
of the solar system as distinctly as we see Jupiter or Mars 
when in opposition, the scene presented to us would not 
indicate the real aspect of the solar system at that, or in- 
deed at any definite instant. Precisely as a daily news- 
paper gives us a later account of what is going on in 
London than of events happening in the provinces, of 
these than of events on the Continent, and of these again 
than of occurrences taking place in America, Asia, Africa, 
or Australasia, so the intelligence brought by light re- 
specting the various members of the solar system belongs 
to different epochs. If man had powers of vision ena- 
bling him to watch what is taking place on the different 
planets of the solar system, it is clear that events of the 
utmost importance might have transpired — under his very 
eyes, so to speak — while yet he remained wholly un- 
conscious of their occurrence. Or, to invert the illustra- 
tion, if an observer on Neptune could see all that is tak- 
ing place on the earth, he might remain for hours quite 
unconscious of an event important enough to affect the 
welfare of a whole continent, though that event should 
happen under his eyes, and his visual powers be such as 
I have supposed. We can imagine, for example, an ob- 
server on Neptune watching the battle of Waterloo from 
the early dawn until the hour when Napoleon's heart was 
yet full of hope, and our great captain was watching with 



SUPERVISION AND CONTROL. 329 

ever-growing anxiety, as charge after charge threatened 
to destroy the squares on whose steadfastness depended 
the fate of a continent. We can conceive how full of 
interest that scene would have been to an intelligent Nep- 
tunian, and how eagerly he would have watched the 
manoeuvres of either army, and also, what neither army 
knew of, the approach of Blucher with his Prussians. 
Yet while our Neptunian would thus have traced the 
progress of the battle from his distant world, the conflict 
would in reality have been long since decided, the final 
charge of the British army accomplished, the Imperial 
Guard destroyed, Napoleon fugitive, and the Prussians, 
who to the Neptunian would be seen still struggling 
through muddy roads toward the field of battle, would 
have been relentlessly pursuing the scattered army of 
France. 

It is, however, when we pass beyond the limits of the 
solar system that the non-contemporaneous nature of the 
scene presented to us becomes most striking. Here we 
have to deal not with seconds, minutes, or hours, but 
with years, decades, and centuries. From the nearest of 
the fixed stars light takes fully three years in travelling to 
the earth. Even the star 61 Cygni is so far from us that 
its light only reaches us in seven years. And so far as 
observation has hitherto gone, it seems unlikely that amid 
the- whole host of heaven there are so many as a hundred 
stars — lucid or telescopic — whose light reaches us in a 
shorter interval of time than twelve or fifteen years. 



330 OTHER WORLDS THAN OURS. 

Whatever views we form as to the arrangement of the 
sidereal scheme, whether those usually accepted be held 
to be correct, or whether I have been right in adopting 
others, there can be no doubt that, among the stars re- 
vealed to us by the telescope, there must be myriads 
which lie many times further from us than the bright 
star in Centaurus and the orb in Cygnus which have 
been found relatively so near. In fact, the views I have 
adopted respecting the wide range of magnitude among 
the fixed stars do not interfere in the least with the the- 
ories which have been formed as to the distances from 
beyond which the light of some of the stars, only just 
visible in powerful telescopes, must be supposed to reach 
us. On the contrary, one may conceive, according to my 
views, that some of these faintly seen orbs may be many 
times larger even than giant Sirius, in which case the dis- 
tance of such stars would be many times greater than 
has been hitherto supposed. We may certainly assume 
with confidence that many stars only visible in powerful 
telescopes shine from beyond depths which light would 
occupy thousands of years in traversing. I cannot, in- 
deed, go further, as astronomers have hitherto done, and 
say that the nebulae must be regarded as external galaxies, 
and therefore as sending their light to us over spaces 
which light must take many times as long an interval in 
traversing as it does in travelling to us from the bounds of 
our own galaxy. But it would be to misinterpret alto- 
gether the views which I have formed respecting the 



SUPERVISION AND CONTROL. 331 

universe to suppose that I imagine those distant spaces 
which astronomers have hitherto filled with imaginary 
galaxies to be untenanted. On the contrary, I have no 
doubt whatever that galaxies resembling our own exist at 
distances infinitely exceeding those at which astronomers 
have placed their most distant nebular universes, if even 
the bounds of our own galaxy do not extend into space 
as far as the widest limits hitherto assigned to the system 
of nebulae. So that I am not precluded from speaking of 
orbs whose light, though unrecognized by us, is yet ever 
pouring in upon the earth, conveying, in letters we can- 
not decipher or even trace, a message which has taken 
millions on millions of years in traversing the awful gulf 
beyond which lie those mysterious realms. 

If we conceive, then, that man's visual powers could 
suddenly be so increased that, without instrumental aid, 
he could look around him into the celestial depths, pierc- 
ing even to those outer galaxies which astronomers have 
seen only imaged in the nebulae, how wide would be the 
range of time presented to him by the wonderful scene he 
would behold ! There would blaze out Alpha Centauri 
with its record three years old ; there the star in Cygnus 
as it existed seven years since ; the whole host of stars 
known to man would exhibit records ranging from a few 
years to many centuries in age ; and lastly, the external 
galaxies, which are perhaps forever hidden from the 
searching gaze of man, would reveal themselves as they 
were ages on ages before man appeared upon the earth, 



332 OTHER WORLDS THAN OURS. 

ages even before this earth was framed into a globe ; nay, 
ages perhaps before the planetary system had begun to 
gather into worlds around its central orb. 

It is when we are thus contemplating in imagination 
the whole expanse of the universe, and as one almost may 
say the whole range of past time, that the author of the 
little treatise I have spoken of invites us to consider two 
processes of thought having sole reference to this earth 
on which we live, and to that history which, though all- 
important to ourselves, seems to fade into such utter 
insignificance in the presence of the grand history of the 
orbs which lie in uncounted millions around us. 

To a being placed on some far-distant orb, whence light 
would occupy thousands of years to wing its flight to us, 
there would be presented, if he turned his gaze upon our 
earth, and if his vision were capable of telling him of her 
aspect, the picture of events which thousands of years 
since really occurred upon her surface. For the light 
which left the earth at that time, winging its way through 
space with the account, if we may so speak, of those oc- 
currences, is now travelling as swiftly as when it left our 
earth, but amid regions of space removed from us by a 
light-journey thousands of years in duration. And thus, 
to the observer on this distant orb, the events which hap- 
pened in the far-off years would seem to be actually in 
progress. 

But now, conceive that powers of locomotion commen- 
surate with his wonderful powers of vision were given to 



SUPERVISION AND CONTROL. 333 

this being, and that in an instant of time he could sweep 
through the enormous interval separating him from our 
earth, until he were no further from us than the moon. 
At the beginning of that tremendous journey he would be 
watching events which were occurring thousands of years 
ago ; at its close he would gaze upon the earth as it was 
one second only before he undertook his instantaneous 
flight; so that, in the course of his journey, he would 
gaze upon a succession of events which had occurred dur- 
ing those thousands of years upon the face of this little 
earth. 

The other conception is less beautiful and striking — I 
may remark, also, that it is, in a scientific sense, some- 
what more exact. Suppose that a being armed with such 
powers of vision as we have imagined should watch from 
the neighborhood of our earth the progress of some inter- 
esting event. If he then began to travel from the earth at 
a rate equal to that at which light travels, he would see 
one phase of the event continually present before him, 
because he would always be where the light-message re- 
cording that event was actually travelling. By passing 
somewhat less swiftly away, he would see the event tak- 
ing place with singular slowness ; while passing away 
more swiftly, he would see the event occurring in inverted 
order. Suppose, for example, he was watching the battle 
of Waterloo — he could gaze on the fine picture presented 
by the Imperial Guard as they advanced upon the Eng- 
lish army, for hours, years, nay, for centuries or cycles ; 



334 OTHER WCELDS THAN OURS. 

or he might watch the whole progress of the charge oc- 
curring so slowly that years might elapse between each 
step of the advancing column, and the bullets which 
mowed down their ranks might either seem unmoving, or 
else appear to wend their way with scarcely perceptible 
motion through the air ; or finally, he might so wing his 
flight through space that the Guard would seem to re- 
treat, their dead men coming to life as the bullets passed 
from their wounds, until at length the Old Guard would 
seem as it was when it began its advance, in the assured 
hope of deciding "Waterloo, as it had already decided s<j 
many hard-fought battles for its imperial chief. 

It may seem hypercritical to notice scientific inexact* 
Hess in ideas professedly fanciful. But as the author lays 
some little stress upon the scientific truth of the method 
jn which his fancies are exhibited, and as, further, he 
dwells upon two of the more obvious objections to the 
first conception, it may be well to consider a further ob- 
jection, which enforces on us a total change in the way of 
presenting the idea. He remarks that the being he has 
conceived to be borne toward the earth through a dis- 
tance so enormous would not see in a moment the whole 
history of the earth during the thousands of years con- 
sidered, but only the history of that hemisphere which 
was turned toward him; while, further, all that took 
place under roofs or under cover of any sort would re- 
main unperceived by him. But there is a more serious 
objection. Among the events which have taken placs 



SUPERVISION AND CONTROL. 335 

during those thousands of years have been thousands of 
revolutions of the earth around the sun, and more than 
365 times as many rotations of the earth upon her axis, 
to say nothing of the stately sway of the earth in her 
motion of precession. So that our imaginary observer 
would in reality see the earth whirling with inconceivable 
rapidity upon its axis, and sweeping with even more 
tremendous velocity around the sun, so as to complete 
thousands of circuits in a single second. He would see 
clouds forming and vanishing in an amazing succession of 
changes, all occurring in a single instant. And even 
though his powers of vision enabled him to pierce the 
cloud-envelope, he would not have a consecutive present- 
ment of the various events occurring in any part of the 
earth, but only a hap-hazard succession of half-days for 
each portion of her surface. 

However, we can easily see that, by a slight modifica- 
tion, the beautiful conception of our author can be made 
to illustrate one mode at least in which the events occur- 
ring upon our earth may be conceived to be at all times 
present to the thoughts of an Omnipresent Being. Im- 
agine a sphere with a radius over which light would 
travel in the time which has elapsed since living creat- 
ures first began to move upon this earth, and having for 
centre the place occupied by the earth at that instant. 
Then, if we imagine millions of eyes over the surface of 
that sphere, all turned with piercing powers of vision 
upon the central earth, we see that to these eyes the 



336 OTHER WORLDS THAN OURS. 

earth would be presented by the record of light, not as 
she is now, but as she was at that primeval day. Now, 
conceive those millions of eyes closing swiftly in upon 
the earth, but with this peculiarity of movement, that, 
instead of being always on a sphere around a fixed point, 
they were always on a sphere around the position which 
was really occupied by the earth when the light-messages 
started which those eyes were receiving at the moment. 
Then if that wondrous sphere contracted in an instant, 
according to the law assigned it, until its myriad mill- 
ions of eyes were gazing intently on our earth from a 
sphere of but a few thousand miles in radius, the whole 
history of the earth, so far as light could render it, would 
have been in a moment of time presented before the 
myriad-eyed sphere. 

By extending these considerations to other modes in 
which the history of an event is recorded, so to speak, 
by natural processes, we can see that a much more com- 
plete and definite picture of past events than light can 
convey must be at all times present in the universe. A 
sense which could analyze heat-impressions as eyesight 
analyzes light would tell us not only what eyesight tells 
us, but much that no light-messages can convey to us. 
At least it is conceivable that a sense of this sort would 
enable the being provided with it to recognize not 
merely the nature of the surface of any body whose heat 
reached the organ of this sense, but the quality of the 
body's internal structure, processes going on within the 



SUPERVISION AND OONTROL. 337 

body, or the nature of bodies so placed that eyesight 
would not render us sensible even of their existence. 
Electricity, in like manner, would avail to give informa- 
tion altogether distinct from that which light can impart. 

But again, the senses by which we judge of what is 
going on around us are, after all, merely certain means by 
which we judge of causes by their effects. When we say, 
for instance, that we have seen such and such an object, 
or watched such and such an event, what we really imply 
is that we have recognized certain physical impressions 
which we can only explain by the existence of that object, 
or by the occurrence of that event. We know, in fact, 
that in certain exceptional cases impressions resembling 
those caused by the actual presence of an object, or by 
the actual occurrence of some event, may arise where no 
such object has been present, or where no such event has 
taken place. Still, we commonly feel safe from error in 
concluding, from certain impressions conveyed to the 
mind by the agency of the senses that certain objects 
have been really present, at rest or in action, before us. 

But then, even man, limited as are his powers, can yet 
follow a series of effects and causes far more numerous 
than those concerned in the act of vision ; and so he can 
become certain of the occurrence of past events of which 
no sense he possesses gives him any direct information. 
For example, though I neither saw the battle of Waterloo 
nor heard the thunder of the guns there, yet I am as cer- 
tain that the battle really took place as though sight and 



338 OTHER WORLDS THAN OURS. 

hearing had given me direct information on the matter. 
And when I inquire whence that certainty arises, I find a 
complicated series of events involved in mj acquisition 
of the knowledge that the battle took place. My inter- 
pretation of the letterpress account of the battle involved 
in itself a number of more or less complex relations, 
associated with the question of my confidence in those 
who taught me that certain symbols represented certain 
letters, that certain combinations of letters represented 
certain words, and that certain words represented certain 
ideas. Not to follow out the long train of thoughts thus 
suggested, it will be clear that, with regard to a variety of 
matters, the knowledge which any man has is associated 
with consideration of cause and effect, of general experi- 
ence, of confidence in the accounts of others or in his 
own judgment, which are in reality of a highly complex 
character. 

Now, we are led by these thoughts to remember that 
independently of those records of past events which are 
continually present throughout the universe in processes 
resembling those which directly affect our senses, such 
events leave their record (even to their minutest details) 
in the consequences to which they have led. If a great 
naturalist like Huxley or Owen can tell by examining the 
tooth of a creature belonging to some long-extinct race, 
not only what the characteristics of that race were, but 
the general nature of the scenery amid which such creat- 
ures lived, we see at once that a single grain of sand or a 



SUPERVISION AN3 CONTROL. 33 

drop of water must convey to an Omniscient and Omni- 
present Being the history of the whole world of which it 
forms part. Nay, why should we pause here ? The his- 
tory of that world is in truth bound up so intimately with 
the history of the universe, that the grain of sand or drop 
of water conveys not only the history of the world, but 
with equal completeness the history of the whole uni- 
verse. In fact, if we consider the matter attentively, we 
see that there cannot be a single atom throughout space 
which could have attained its present exact position and 
state, had the history of any part of the universe, how- 
ever insignificant, been otherwise than it has actually been, 
in even the minutest degree. 

Turning from the past to the future, we must not let 
the limited nature of our recognition of the course of 
future events prevent us from forming a just opinion as 
to the way in which the future is in a sense always pres- 
ent. We can judge of the past by its effects, but we are 
almost utterly unable to judge of the future by its causes. 
Yet we cannot doubt that the future is present in its 
germs, precisely as the past is present in its fruits. It 
may be regarded in fact as merely a peculiarity of man's 
constitution that the past is more clearly present to his 
mental vision than the future. It is easy not only to 
conceive that the future and the past should be equally 
present to intelligent creatures, but to conceive of a form 
of intelligence according to which past events would be 
obliterated from the mind as fast as they took place, 



340 OTHER WORLDS THAN OVKtL 

while the future should be as actually present as to th$ 
ordinary human mind the past is. 

In considering the Omniscient Omnipresent Being, 
however, all questions of degree must be set on one side. 
The future must be absolutely and essentially present to 
such a Being in its germs as the past has been shown to 
be in its fruits. If a grain of sand contains in its state, 
figure, and position, the picture of the universe as it is, 
and the whole history of the universe throughout the in- 
finite past — and who can doubt that this is so ? — it con- 
tains with equal completeness the history of the universe 
throughout the infinite future. No other view is com- 
patible with the assumption of infinite wisdom, and no 
assumption which limits the wisdom of a Ruler of an in- 
finite universe is compatible with our belief in the fitness 
of such a Buler to reign supreme over the universe. 

Obviously also every event, however trifling, must be 
held to contain in itself the whole history of the uni- 
verse throughout the infinite past and throughout the in- 
finite future. For every event, let its direct importance 
be what it may, is indissolubly bound up with events 
preceding, accompanying, and following it, in endless 
series of causation, interaction, and effect. 

So far, then, as the supervision of a Ruler over the 
universe is concerned, we have two lines of thought, each 
leading to the recognition of perfect supervision. In 
virtue (1) of the omnipresence, and (2) of the infinite 
wisdom of such a Ruler, He could see at each instant $w* 



SUPERVISION AND CONTROL. 341 

whole universe as it has been in the infinite past, as it is 
now, and as it will be in the infinite future; and this 
being as true of any one instant as it is of any other, we 
recognize the operation of yet a new form of infinity — the 
infinite duration of the Euler's existence — to render yet 
more inconceivably perfect His supervision of the uni- 
verse. 

With regard to control it need hardly be said that if a 
Buler does exercise control, apart from the laws assigned 
to His universe, His knowledge of the progress of past 
and future events would not therefore be called in ques- 
laon, since His own direct action, whether in the past or 
in the future, would be quite as much the subject of His 
consciousness (to use this word for want of a better) as 
the action of His creatures or of the laws He had pri- 
marily set them. 

We know that certain laws have been assigned to the 
universe, and we know, also, that, so far as our very lim- 
ited experience enables us to determine, these laws are 
never abrogated. Here I set altogether aside, for the 
moment, the possibility of miracles (since miracles would 
necessarily be non-natural events), and consider only the 
results of experimental or observational science. Thus we 
are led to the conclusion that all things happen according 
to set physical laws; and we see strong reason to believe 
that these laws are sufficient for the control of all things. 

Now it seems conceivable that in reality it is only our 
limited acquaintance with the operation of the laws of the 



342 OTHER WORLDS THAN OURS, 

universe which makes us regard them as unchanging, and, 
so to speak, inexorable. But I think that this view — 
though it has been entertained by many thoughtful men 
— is in reality inconsistent with just conceptions of in- 
finite wisdom. If the wisdom of a Ruler of the universe, 
though inconceivably great, were yet finite, we could not 
suppose that the universe would have been so planned 
(still to use inexact words for want of better), and laws of 
such a nature assigned to it, that throughout the infinity 
of time all things should work welL There would then, 
undoubtedly, be continual need of adaptation, change, and 
remodelling — of the annulment of a law here, or its sus- 
pension there — in order that the whole might not fall to 
rack. But with a Ruler infinitely wise, there should be 
no such necessity. The whole scheme of the universe 
would be so perfect that direct intervention would not at 
any time be required. 

To sum up, we perceive that, before a Ruler omnipres- 
ent, omniscient, and omnipotent, the infinite past and the 
infinite future of the universe would be at all times sen- 
sibly present ; that each the minutest atom and every the 
least important event would exhibit before Him at each 
instant the perfect history of the limitless past and future 
of the universe ; and lastly, that His infinitely perfect con- 
sciousness of the control over all that has been, is, or will 
be, would be infinitely multiplied (to use the only available 
expression) by the infinite duration throughout which Hia 
existence would extend. 



OCT 20 1902 



LIBRARY OF CONGRESS 




003 629 873 A 



